Curcumin for COVID-19: real-time meta analysis of 27 studies
Abstract
Statistically significant lower risk is seen for mortality, ventilation, hospitalization, progression, recovery, and viral clearance. 18 studies from 16 independent teams in 8 countries show significant
improvements.
Meta analysis using the most serious outcome reported shows
41% [30‑51%] lower risk. Results are similar for Randomized Controlled Trials, higher quality studies, and peer-reviewed studies.
Results are very robust — in exclusion sensitivity analysis 26 of
27 studies must be excluded to avoid finding statistically significant
efficacy in pooled analysis.
Studies typically use advanced formulations for greatly improved bioavailability.
No treatment or intervention
is 100% effective. All practical, effective, and safe means should be used
based on risk/benefit analysis.
Multiple treatments are typically used
in combination, and other treatments
may be more effective.
The quality of non-prescription supplements can vary widely1,2.
Curcumin for COVID-19 — Highlights
Curcumin reduces
risk with very high confidence for mortality, hospitalization, recovery, and in pooled analysis, high confidence for ventilation, progression, and viral clearance, and low confidence for ICU admission.
Studies typically use advanced formulations for greatly improved bioavailability.
15th treatment shown effective with ≥3 clinical studies in
February 2021, now with p = 0.0000000096 from 27 studies.
Outcome specific analyses and combined evidence from all
studies, incorporating treatment delay, a primary confounding factor.
Real-time updates and corrections,
transparent analysis with all results in the same format, consistent protocol
for 109
treatments.
Figure 1.
A. Random effects
meta-analysis. This plot shows pooled effects,
see the specific outcome analyses for individual outcomes.
Analysis validating pooled outcomes for
COVID-19 can be found below.
Effect extraction is pre-specified, using the most serious outcome reported.
For details see the appendix.
B. Timeline of results in curcumin studies. The marked dates indicate the time when efficacy was known with a statistically significant improvement of ≥10% from ≥3 studies for pooled outcomes, one or more specific outcome, pooled outcomes in RCTs, and one or more specific outcome in RCTs. Efficacy based on RCTs only was delayed by 2.9 months, compared to using all studies. Efficacy based on specific outcomes was delayed by 2.4 months, compared to using pooled outcomes.
SARS-CoV-2 infection primarily begins in the upper respiratory
tract and may progress to the lower respiratory tract, other tissues, and the
nervous and cardiovascular systems, which may lead to cytokine storm,
pneumonia, ARDS, neurological injury7-17 and
cognitive deficits9,14, cardiovascular
complications18-20, organ failure, and death.
Minimizing replication as early as possible is recommended.
SARS-CoV-2 infection and replication involves the complex interplay of 50+
host and viral proteins and other factorsA,21-26, providing many
therapeutic targets for which many existing compounds have known activity.
Scientists have predicted that over 8,000 compounds may
reduce COVID-19 risk27, either by
directly minimizing infection or replication, by supporting immune system
function, or by minimizing secondary complications.
In Silico studies predict inhibition of SARS-CoV-2 with curcumin or metabolites via binding to the spikeB,28-32 (and specifically the receptor binding domainC,33-35), MproD,29,30,32,34-43, RNA-dependent RNA polymeraseE,35,44, ACE2F,31,42,45, nucleocapsidG,46,47, nsp10H,47, and helicaseI,48 proteins.
In Vitro studies demonstrate inhibition of the spikeB,49 (and specifically the receptor binding domainC,50), MproD,43,49,51,52, ACE2F,50, and TMPRSS2J,50 proteins, and inhibition of spike-ACE2 interactionK,53.
In Vitro studies demonstrate efficacy in Calu-3L,54, A549M,49, 293TN,55, HEK293-hACE2O,52,56, 293T/hACE2/TMPRSS2P,57, Vero E6Q,30,35,40,49,54,56,58-60 , and SH-SY5YR,61 cells.
Curcumin is predicted to inhibit the interaction between the SARS-CoV-2 spike protein receptor binding domain and the human ACE2 receptor for the delta and omicron variants33, decreases pro-inflammatory cytokines induced by SARS-CoV-2 in peripheral blood mononuclear cells60, alleviates SARS-CoV-2 spike protein-induced mitochondrial membrane damage and oxidative stress55, may limit COVID-19 induced cardiac damage by inhibiting the NF-κB signaling pathway which mediates the profibrotic effects of the SARS-CoV-2 spike protein on cardiac fibroblasts19, and inhibits SARS-CoV-2 ORF3a ion channel activity, which contributes to viral pathogenicity and cytotoxicity62.
We analyze all significant
controlled studies of
curcumin
for COVID-19.
Search methods, inclusion criteria, effect extraction criteria (more serious
outcomes have priority), all individual study data, PRISMA answers, and
statistical methods are detailed in Appendix 1. We present random
effects meta-analysis results for all studies, studies within each treatment stage, individual outcomes, peer-reviewed studies, Randomized Controlled Trials (RCTs), and higher quality studies.
Figure 2 shows stages of possible treatment for
COVID-19. Prophylaxis refers to regularly taking medication before
becoming sick, in order to prevent or minimize infection. Early
Treatment refers to treatment immediately or soon after symptoms appear,
while Late Treatment refers to more delayed treatment.
Figure 2. Treatment stages.
Table 1 shows potential mechanisms of action for
the treatment of COVID-19 using curcumin.
| 3CLpro inhibitor | Curcumin inhibits SARS-CoV-2 3CLpro29,30,34-43,49,51, |
| RdRp inhibitor | SARS-CoV-2 RNA‐dependent RNA polymerase (RdRp) inhibition35,44. |
| ACE2 inhibitor | Curcumin inhibits ACE2 activity. SARS-CoV-2 viral entry requires host cell surface proteins ACE2 and TMPRSS263,64. |
| TMPRSS2 downregulation | Curcumin downregulates transmembrane serine protease 2 (TMPRSS2). SARS-CoV-2 viral entry requires host cell surface proteins ACE2 and TMPRSS250. |
| Cathepsin L inhibitor | Curcumin inhibits cathepsin L activity. Cathepsin L plays a key role in viral entry50. |
| Anti‑inflammatory | Curcumin shows anti-inflammatory effects60,65-69. |
| Inhibition in Vero E6 cells demonstrated | In Vitro research shows curcumin inhibits SARS-CoV-2 in Vero E6 cells30,35,40,49,54, |
| Inhibition in Calu-3 cells demonstrated | In Vitro research shows curcumin inhibits SARS-CoV-2 in Calu-3 cells54. |
In Silico studies predict inhibition of SARS-CoV-2 with curcumin or metabolites via binding to the spikeB,28-32 (and specifically the receptor binding domainC,33-35), MproD,29,30,32,34-43, RNA-dependent RNA polymeraseE,35,44, ACE2F,31,42,45, nucleocapsidG,46,47, nsp10H,47, and helicaseI,48 proteins.
In Vitro studies demonstrate inhibition of the spikeB,49 (and specifically the receptor binding domainC,50), MproD,43,49,51,52, ACE2F,50, and TMPRSS2J,50 proteins, and inhibition of spike-ACE2 interactionK,53.
In Vitro studies demonstrate efficacy in Calu-3L,54, A549M,49, 293TN,55, HEK293-hACE2O,52,56, 293T/hACE2/TMPRSS2P,57, Vero E6Q,30,35,40,49,54,56,58-60 , and SH-SY5YR,61 cells.
Curcumin is predicted to inhibit the interaction between the SARS-CoV-2 spike protein receptor binding domain and the human ACE2 receptor for the delta and omicron variants33, decreases pro-inflammatory cytokines induced by SARS-CoV-2 in peripheral blood mononuclear cells60, alleviates SARS-CoV-2 spike protein-induced mitochondrial membrane damage and oxidative stress55, may limit COVID-19 induced cardiac damage by inhibiting the NF-κB signaling pathway which mediates the profibrotic effects of the SARS-CoV-2 spike protein on cardiac fibroblasts19, and inhibits SARS-CoV-2 ORF3a ion channel activity, which contributes to viral pathogenicity and cytotoxicity62.
An In Vivo animal study supports the efficacy of curcumin32.
4 studies investigate novel formulations of curcumin that may be more
effective for COVID-1935,74,76,77.
Preclinical research is an important part of the development of
treatments, however results may be very different in clinical trials.
Preclinical results are not used in this paper.
Table 2 summarizes the results for all stages combined, for Randomized Controlled Trials, for peer-reviewed studies, after exclusions, and for specific outcomes.
Table 3 shows results by treatment stage.
Figure 3 plots individual results by treatment stage.
Figure 4, 5, 6, 7, 8, 9, 10, 11, and 12
show forest plots for random effects meta-analysis of
all studies with pooled effects, mortality results, ventilation, ICU admission, hospitalization, progression, recovery, viral clearance, and peer reviewed studies.
| Improvement | Studies | Patients | Authors | |
|---|---|---|---|---|
| All studies | 41% [30‑51%] **** | 27 | 14,886 | 240 |
| After exclusions | 39% [27‑49%] **** | 25 | 14,573 | 220 |
| Peer-reviewed studiesPeer-reviewed | 41% [29‑51%] **** | 26 | 14,640 | 234 |
| Randomized Controlled TrialsRCTs | 44% [29‑56%] **** | 21 | 1,712 | 200 |
| Mortality | 63% [36‑78%] *** | 8 | 714 | 83 |
| VentilationVent. | 80% [25‑95%] * | 4 | 435 | 30 |
| ICU admissionICU | 78% [-27‑96%] | 2 | 169 | 18 |
| HospitalizationHosp. | 27% [18‑35%] **** | 12 | 13,478 | 92 |
| Recovery | 40% [27‑51%] **** | 16 | 1,109 | 140 |
| Viral | 37% [10‑56%] * | 6 | 389 | 46 |
| RCT mortality | 63% [36‑78%] *** | 8 | 714 | 83 |
| RCT hospitalizationRCT hosp. | 20% [9‑29%] *** | 7 | 557 | 59 |
| Early treatment | Late treatment | Prophylaxis | |
|---|---|---|---|
| All studies | 29% [12‑43%] ** | 51% [39‑61%] **** | 36% [11‑55%] ** |
| After exclusions | 29% [12‑43%] ** | 50% [34‑63%] **** | 37% [6‑58%] * |
| Peer-reviewed studiesPeer-reviewed | 29% [12‑43%] ** | 54% [40‑64%] **** | 36% [11‑55%] ** |
| Randomized Controlled TrialsRCTs | 26% [7‑41%] ** | 54% [40‑64%] **** | |
| Mortality | 84% [39‑96%] ** | 56% [19‑76%] ** | |
| VentilationVent. | 72% [-65‑95%] | 88% [3‑98%] * | |
| ICU admissionICU | 78% [-27‑96%] | ||
| HospitalizationHosp. | 30% [7‑48%] * | 24% [13‑34%] *** | 37% [6‑58%] * |
| Recovery | 30% [16‑42%] *** | 58% [37‑72%] **** | |
| Viral | 36% [-26‑67%] | 43% [22‑58%] *** | |
| RCT mortality | 84% [39‑96%] ** | 56% [19‑76%] ** | |
| RCT hospitalizationRCT hosp. | 32% [-69‑73%] | 22% [10‑33%] *** |
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Figure 3. Scatter plot showing the most serious outcome in all studies, and for studies within each stage. Diamonds shows the results of random effects meta-analysis.
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Figure 4. Random effects meta-analysis for all studies.
This plot shows pooled effects,
see the specific outcome analyses for individual outcomes.
Analysis validating pooled outcomes for
COVID-19 can be found below.
Effect extraction is pre-specified, using the most serious outcome reported.
For details see the appendix.
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Figure 5. Random effects meta-analysis for mortality results.
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Figure 6. Random effects meta-analysis for ventilation.
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Figure 7. Random effects meta-analysis for ICU admission.
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Figure 8. Random effects meta-analysis for hospitalization.
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Figure 9. Random effects meta-analysis for progression.
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Figure 10. Random effects meta-analysis for recovery.
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Figure 11. Random effects meta-analysis for viral clearance.
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Figure 12. Random effects meta-analysis for peer reviewed studies.
Effect extraction is pre-specified, using the most serious outcome reported,
see the appendix for details.
Analysis validating pooled outcomes for
COVID-19 can be found below.
Zeraatkar et al. analyze 356 COVID-19 trials, finding no significant
evidence that preprint results are inconsistent with peer-reviewed studies.
They also show extremely long peer-review delays, with a median of 6 months to
journal publication. A six month delay was equivalent to around 1.5 million
deaths during the first two years of the pandemic. Authors recommend using
preprint evidence, with appropriate checks for potential falsified data, which
provides higher certainty much earlier. Davidson et al. also showed no
important difference between meta analysis results of preprints and
peer-reviewed publications for COVID-19, based on 37 meta analyses including
114 trials.
Figure 13 shows a comparison of results for RCTs and non-RCT studies.
Random effects meta analysis of RCTs shows
44% improvement,
compared to 36% for other studies.
Figure 14, 15, and 16
show forest plots for random effects meta-analysis of
all Randomized Controlled Trials, RCT mortality results, and RCT hospitalization results.
RCT results are included in Table 2 and Table 3.
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Figure 13. Results for RCTs and non-RCT studies.
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Figure 14. Random effects meta-analysis for all Randomized Controlled Trials.
This plot shows pooled effects,
see the specific outcome analyses for individual outcomes.
Analysis validating pooled outcomes for
COVID-19 can be found below.
Effect extraction is pre-specified, using the most serious outcome reported.
For details see the appendix.
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Figure 15. Random effects meta-analysis for RCT mortality results.
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Figure 16. Random effects meta-analysis for RCT hospitalization results.
RCTs help to make study groups more similar and can provide a higher level of
evidence, however they are subject to many biases80, and
analysis of double-blind RCTs has identified extreme levels of bias81.
For COVID-19, the overhead may delay treatment, dramatically compromising
efficacy; they may encourage monotherapy for simplicity at the cost of
efficacy which may rely on combined or synergistic effects; the participants
that sign up may not reflect real world usage or the population that benefits
most in terms of age, comorbidities, severity of illness, or other factors;
standard of care may be compromised and unable to evolve quickly based on
emerging research for new diseases; errors may be made in randomization and
medication delivery; and investigators may have hidden agendas or vested
interests influencing design, operation, analysis, reporting, and the
potential for fraud. All of these biases have been observed with COVID-19
RCTs. There is no guarantee that a specific RCT provides a higher level of
evidence.
RCTs are expensive and many RCTs are funded
by pharmaceutical companies or interests closely aligned with pharmaceutical
companies. For COVID-19, this creates an incentive to show efficacy for
patented commercial products, and an incentive to show a lack of efficacy for
inexpensive treatments. The bias is expected to be significant, for example
Als-Nielsen et al. analyzed 370 RCTs from Cochrane reviews, showing that
trials funded by for-profit organizations were 5 times more likely to
recommend the experimental drug compared with those funded by nonprofit
organizations. For COVID-19, some major philanthropic organizations are
largely funded by investments with extreme conflicts of interest for and
against specific COVID-19 interventions.
High quality RCTs for novel acute diseases are more challenging, with
increased ethical issues due to the urgency of treatment, increased risk due
to enrollment delays, and more difficult design with a rapidly evolving
evidence base. For COVID-19, the most common site of initial infection is the
upper respiratory tract. Immediate treatment is likely to be most successful
and may prevent or slow progression to other parts of the body. For a
non-prophylaxis RCT, it makes sense to provide treatment in advance and
instruct patients to use it immediately on symptoms, just as some governments
have done by providing medication kits in advance. Unfortunately, no RCTs have
been done in this way. Every treatment RCT to date involves delayed treatment.
Among the 109 treatments we have analyzed,
65% of RCTs involve very late treatment 5+ days after
onset. No non-prophylaxis COVID-19 RCTs match the potential real-world use of
early treatments. They may more accurately represent results for treatments
that require visiting a medical facility, e.g., those requiring intravenous
administration.
For COVID-19, observational study results do not systematically
differ from RCTs, RR 1.00 [0.92‑1.08]
across 109 treatments83.
Evidence shows that observational studies
can also provide reliable results. Concato et al. found that well-designed
observational studies do not systematically overestimate the magnitude of the
effects of treatment compared to RCTs. Anglemyer et al. analyzed reviews
comparing RCTs to observational studies and found little evidence for
significant differences in effect estimates.
We performed a similar analysis across the 109 treatments
we cover, showing no significant difference in the results of RCTs compared to
observational studies, RR 1.00 [0.92‑1.08]. Similar results are found for all low-cost treatments, RR
1.02 [0.92‑1.12]. High-cost treatments
show a non-significant trend towards RCTs showing greater efficacy,
RR 0.92 [0.82‑1.03].
Details can be found in the
supplementary data.
Lee et al. showed that only 14% of the guidelines of the Infectious
Diseases Society of America were based on RCTs. Evaluation of studies relies
on an understanding of the study and potential biases. Limitations in an RCT
can outweigh the benefits, for example excessive dosages, excessive treatment
delays, or remote survey bias may have a greater effect on results. Ethical
issues may also prevent running RCTs for known effective treatments. For more
on issues with RCTs see87,88.
Currently, 48 of the treatments we analyze show statistically significant efficacy or harm, defined as ≥10% decreased risk or >0% increased risk from ≥3 studies. Of these, 60% have been confirmed in RCTs, with a mean delay of 7.1 months (68% with 8.2 months delay for low-cost treatments). The remaining treatments either have no RCTs, or the point estimate is consistent.
We need to
evaluate each trial on its own merits. RCTs for a given medication and disease
may be more reliable, however they may also be less reliable. For off-patent
medications, very high conflict of interest trials may be more likely to be
RCTs, and more likely to be large trials that dominate meta analyses.
To avoid bias in the selection of studies, we analyze all
non-retracted studies. Here we show the results after excluding
studies with major issues likely to alter results, non-standard studies, and
studies where very minimal detail is currently available. Our bias evaluation
is based on analysis of each study and identifying when there is a significant
chance that limitations will substantially change the outcome of the study. We
believe this can be more valuable than checklist-based approaches such as
Cochrane GRADE, which can be easily influenced by potential bias, may ignore
or underemphasize serious issues not captured in the checklists, and may
overemphasize issues unlikely to alter outcomes in specific cases (for example
certain specifics of randomization with a very large effect size and
well-matched baseline characteristics).
The studies excluded are as below.
Figure 17 shows a forest plot for random
effects meta-analysis of all studies after exclusions.
Hartono, randomization resulted in significant baseline differences that were not adjusted for.
Shehab, unadjusted results with no group details.
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Figure 17. Random effects meta-analysis for all studies after exclusions.
This plot shows pooled effects,
see the specific outcome analyses for individual outcomes.
Analysis validating pooled outcomes for
COVID-19 can be found below.
Effect extraction is pre-specified, using the most serious outcome reported.
For details see the appendix.
Heterogeneity in COVID-19 studies arises from many factors including:
The time
between infection or the onset of symptoms and treatment may critically affect
how well a treatment works. For example an antiviral may be very effective
when used early but may not be effective in late stage disease, and may even
be harmful. Oseltamivir, for example, is generally only considered effective
for influenza when used within 0-36 or 0-48 hours91,92.
Baloxavir marboxil studies for influenza also show that treatment delay is critical
— Ikematsu et al. report an 86% reduction in cases for post-exposure
prophylaxis, Hayden et al. show a 33 hour reduction in the time to
alleviation of symptoms for treatment within 24 hours and a reduction of 13
hours for treatment within 24-48 hours, and Kumar et al. report only 2.5
hours improvement for inpatient treatment.
| Treatment delay | Result |
| Post-exposure prophylaxis | 86% fewer cases93 |
| <24 hours | -33 hours symptoms94 |
| 24-48 hours | -13 hours symptoms94 |
| Inpatients | -2.5 hours to improvement95 |
Figure 18 shows a mixed-effects meta-regression for efficacy
as a function of treatment delay in COVID-19 studies from 109 treatments, showing
that efficacy declines rapidly with treatment delay. Early treatment is
critical for COVID-19.
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Figure 18. Early treatment is more effective. Meta-regression showing efficacy as a function of treatment delay in COVID-19 studies from 109 treatments.
Details of the patient population including age and comorbidities may
critically affect how well a treatment works. For example, many COVID-19
studies with relatively young low-comorbidity patients show all patients
recovering quickly with or without treatment. In such cases, there is little
room for an effective treatment to improve results, for example as in
López-Medina et al.
Efficacy may
depend critically on the distribution of SARS-CoV-2 variants encountered by
patients. Risk varies significantly across variants97, for
example the Gamma variant shows significantly different characteristics98-101. Different mechanisms of action may be
more or less effective depending on variants, for example the degree to which
TMPRSS2 contributes to viral entry can differ across variants102,103.
Effectiveness may depend strongly on the dosage and treatment regimen.
The use
of other treatments may significantly affect outcomes, including supplements,
other medications, or other interventions such as prone positioning.
Treatments may be synergistic104-115, therefore
efficacy may depend strongly on combined treatments.
The
quality of medications may vary significantly between manufacturers and
production batches, which may significantly affect efficacy and safety.
Williams et al. analyze ivermectin from 11 different sources, showing
highly variable antiparasitic efficacy across different manufacturers.
Xu et al. analyze a treatment from two different manufacturers, showing 9
different impurities, with significantly different concentrations for each
manufacturer.
Non-prescription supplements may show very wide variations in quality1,2.
Across all
studies there is a strong association between different outcomes, for example
improved recovery is strongly associated with lower mortality. However,
efficacy may differ depending on the effect measured, for example a treatment
may be more effective against secondary complications and have minimal effect
on viral clearance.
The
distribution of studies will alter the outcome of a meta analysis. Consider a
simplified example where everything is equal except for the treatment delay,
and effectiveness decreases to zero or below with increasing delay. If there
are many studies using very late treatment, the outcome may be negative, even
though early treatment is very effective.
All meta analyses combine heterogeneous studies, varying in population,
variants, and potentially all factors above, and therefore may obscure
efficacy by including studies where treatment is less effective. Generally, we
expect the estimated effect size from meta analysis to be less than that for
the optimal case.
Looking at all studies is valuable for providing an overview of all research,
important to avoid cherry-picking, and informative when a positive result is
found despite combining less-optimal situations. However, the resulting
estimate does not apply to specific cases such as
early treatment in high-risk populations.
While we present results for all studies, we also present treatment time and
individual outcome analyses, which may be more informative for specific use
cases.
This section validates the use of pooled effects for COVID-19, which enables
earlier detection of efficacy, however note that pooled effects are no longer
required for curcumin as of May 2021.
Efficacy is now known for curcumin based on specific outcomes for all studies and when restricted to RCTs. Efficacy based on specific outcomes was delayed by 2.4 months, compared to using pooled outcomes.
For COVID-19, delay in clinical results translates into
additional death and morbidity, as well as additional economic and societal
damage. Combining the results of studies reporting different outcomes is
required.
There may be no mortality in a trial with low-risk patients,
however a reduction in severity or improved viral clearance may translate
into lower mortality in a high-risk population.
Different studies may report lower severity, improved recovery, and lower mortality,
and the significance may be very high when combining the results.
"The studies reported different outcomes"
is not a good reason for disregarding results.
We present both specific outcome and pooled analyses.
In order to combine the results of studies reporting different outcomes we use
the most serious outcome reported in each study, based on the thesis that
improvement in the most serious outcome provides comparable measures of
efficacy for a treatment. A critical advantage of this approach is
simplicity and transparency.
There are many other ways to combine evidence for different outcomes, along
with additional evidence such as dose-response relationships, however these
increase complexity.
Another way to view pooled analysis is that we are using more of
the available information. Logically we should, and do, use additional
information. For example dose-response and
treatment delay-response relationships provide significant additional evidence
of efficacy that is considered when reviewing the evidence for a
treatment.
Trials with high-risk patients may be restricted due to ethics for treatments
that are known or expected to be effective, and they increase difficulty for
recruiting. Using less severe outcomes as a proxy for more serious outcomes
allows faster collection of evidence.
For many COVID-19 treatments, a reduction in mortality logically
follows from a reduction in hospitalization, which follows from a reduction in
symptomatic cases, which follows from a reduction in PCR positivity. We can
directly test this for COVID-19.
Analysis of the the association between different outcomes across studies from
all 109
treatments we cover confirms the validity of pooled outcome analysis for COVID-19.
Figure 19 shows that lower hospitalization is very strongly associated
with lower mortality (p < 0.000000000001).
Similarly, Figure 20 shows that improved recovery is very strongly associated
with lower mortality (p < 0.000000000001).
Considering the extremes, Singh (D) et al. show an association between viral clearance and
hospitalization or death, with p = 0.003 after excluding one large
outlier from a mutagenic treatment, and based on 44 RCTs including 52,384
patients.
Figure 21 shows that improved viral clearance is strongly associated
with fewer serious outcomes. The association is very similar to
Singh (D) et al., with higher confidence due to the larger number of
studies. As with Singh (D) et al., the confidence increases
when excluding the outlier treatment, from p = 0.00000042 to p = 0.00000002.
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Figure 19. Lower hospitalization is associated with lower mortality, supporting pooled outcome analysis.
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Figure 20. Improved recovery is associated with lower mortality, supporting pooled outcome analysis.
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Figure 19. Improved viral clearance is associated with fewer serious outcomes, supporting pooled outcome analysis.
Currently, 48 of the treatments we analyze show statistically significant efficacy or harm, defined as ≥10% decreased risk or >0% increased risk from ≥3 studies. 89% of these have been confirmed with one or more specific outcomes, with a mean delay of 5.1 months. When restricting to RCTs only, 56% of treatments showing statistically significant efficacy/harm with pooled effects have been confirmed with one or more specific outcomes, with a mean delay of 6.4 months.
Figure 22 shows when treatments were found effective during the
pandemic. Pooled outcomes often resulted in earlier detection of efficacy.
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Figure 22. The time when studies showed that
treatments were effective, defined as statistically significant improvement of
≥10% from ≥3 studies.
Pooled results typically show efficacy earlier than specific
outcome results. Results from all studies often shows efficacy much earlier
than when restricting to RCTs.
Results reflect conditions as used in trials to date, these depend on the
population treated, treatment delay, and treatment regimen.
Pooled analysis could hide efficacy, for example a treatment that is
beneficial for late stage patients but has no effect on viral clearance may
show no efficacy if most studies only examine viral clearance. In practice, it
is rare for a non-antiviral treatment to report viral clearance and to not
report clinical outcomes; and in practice other sources of heterogeneity such
as difference in treatment delay is more likely to hide efficacy.
Analysis validates the use of pooled effects and shows significantly faster
detection of efficacy on average.
However, as with all meta analyses, it is important to review the different
studies included. We also present individual outcome analyses, which may be
more informative for specific use cases.
Publishing is often biased
towards positive results, however evidence suggests that there may be a negative bias for
inexpensive treatments for COVID-19. Both negative and positive results are
very important for COVID-19, media in many countries prioritizes negative
results for inexpensive treatments (inverting the typical incentive for
scientists that value media recognition), and there are many reports of
difficulty publishing positive results119-122.
For curcumin, there is currently not
enough data to evaluate publication bias with high confidence.
One method to evaluate bias is to compare prospective vs.
retrospective studies. Prospective studies are more likely to be published
regardless of the result, while retrospective studies are more likely to
exhibit bias. For example, researchers may perform preliminary analysis with
minimal effort and the results may influence their decision to continue.
Retrospective studies also provide more opportunities for the specifics of
data extraction and adjustments to influence results.
Figure 23 shows a scatter plot of
results for prospective and retrospective studies.
40% of retrospective studies
report a statistically significant positive effect for
one or more outcomes, compared to
73% of prospective studies, consistent with a bias toward publishing negative results.
The median effect size for
retrospective studies is 41% improvement,
compared to 62% for prospective
studies, suggesting a potential bias towards publishing results showing lower efficacy.
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Figure 23. Prospective vs. retrospective studies.
The diamonds show the results of random effects meta-analysis.
Funnel
plots have traditionally been used for analyzing publication bias. This is
invalid for COVID-19 acute treatment trials — the underlying assumptions
are invalid, which we can demonstrate with a simple example. Consider a set of
hypothetical perfect trials with no bias. Figure 24 plot A
shows a funnel plot for a simulation of 80 perfect trials, with random group
sizes, and each patient's outcome randomly sampled (10% control event
probability, and a 30% effect size for treatment). Analysis shows no asymmetry
(p > 0.05). In plot B, we add a single typical variation in COVID-19 treatment
trials — treatment delay. Consider that efficacy varies from 90% for
treatment within 24 hours, reducing to 10% when treatment is delayed 3 days.
In plot B, each trial's treatment delay is randomly selected. Analysis now
shows highly significant asymmetry, p < 0.0001, with six variants of
Egger's test all showing p < 0.05123-130.
Note that these tests fail even though treatment delay is uniformly
distributed. In reality treatment delay is more complex — each trial has
a different distribution of delays across patients, and the distribution
across trials may be biased (e.g., late treatment trials may be more common).
Similarly, many other variations in trials may produce asymmetry, including
dose, administration, duration of treatment, differences in SOC,
comorbidities, age, variants, and bias in design, implementation, analysis,
and reporting.
Figure 24. Example funnel plot analysis for simulated perfect trials.
Pharmaceutical drug
trials often have conflicts of interest whereby sponsors or trial staff have a
financial interest in the outcome being positive. Curcumin for COVID-19
lacks this because it is an inexpensive and widely available supplement.
In contrast, most COVID-19 curcumin trials have been run by
physicians on the front lines with the primary goal of finding the best
methods to save human lives and minimize the collateral damage caused by
COVID-19. While pharmaceutical companies are careful to run trials under
optimal conditions (for example, restricting patients to those most likely to
benefit, only including patients that can be treated soon after onset when
necessary, and ensuring accurate dosing), not all curcumin trials
represent the optimal conditions for efficacy.
Summary statistics from
meta analysis necessarily lose information. As with all meta analyses, studies
are heterogeneous, with differences
in treatment delay, treatment regimen, patient demographics, variants,
conflicts of interest, standard of care, and other factors. We provide analyses for specific
outcomes and by treatment delay, and we aim to identify key characteristics in
the forest plots and summaries. Results should be viewed in the context of
study characteristics.
Some analyses classify treatment based on early or late
administration, as done here, while others distinguish between mild, moderate,
and severe cases. Viral load does not indicate degree of symptoms — for
example patients may have a high viral load while being asymptomatic. With
regard to treatments that have antiviral properties, timing of treatment is
critical — late administration may be less helpful regardless of
severity.
Details of treatment delay per patient is often not available.
For example, a study may treat 90% of patients relatively early, but the
events driving the outcome may come from 10% of patients treated very late.
Our 5 day cutoff for early treatment may be too conservative, 5 days may be too late in many cases.
Comparison across treatments is confounded by differences in
the studies performed, for example dose, variants, and conflicts of interest.
Trials with conflicts of interest may use designs better suited to the
preferred outcome.
In some cases, the most serious outcome has very few events,
resulting in lower confidence results being used in pooled analysis, however
the method is simpler and more transparent. This is less critical as the
number of studies increases. Restriction to outcomes with sufficient power may
be beneficial in pooled analysis and improve accuracy when there are few
studies, however we maintain our pre-specified method to avoid any
retrospective changes.
Studies show that combinations of treatments can be highly
synergistic and may result in many times greater efficacy than individual
treatments alone104-115.
Therefore standard of care may be critical and benefits may diminish or
disappear if standard of care does not include certain treatments.
This real-time analysis is constantly updated based on
submissions. Accuracy benefits from widespread review and submission of
updates and corrections from reviewers. Less popular treatments may receive
fewer reviews.
No treatment or intervention is 100% available and
effective for all current and future variants. Efficacy may vary significantly
with different variants and within different populations. All treatments have
potential side effects. Propensity to experience side effects may be predicted
in advance by qualified physicians. We do not provide medical advice. Before
taking any medication, consult a qualified physician who can compare all
options, provide personalized advice, and provide details of risks and
benefits based on individual medical history and situations.
1 of the 27
studies compare against other treatments, which may reduce the effect
seen.
10 of 27 studies
combine treatments. The results of
curcumin
alone may differ.
10 of 21 RCTs use combined treatment.
4 other meta analyses show significant improvements with curcumin for mortality3-6, hospitalization3,6, recovery5, and symptoms3.
Many reviews cover curcumin for COVID-19, presenting additional
background on mechanisms, formulations, and related results, including69,131-142.
SARS-CoV-2 infection and replication involves a complex interplay of 50+ host
and viral proteins and other factors21-26,
providing many therapeutic targets.
Over 8,000 compounds have been predicted to reduce COVID-19
risk27, either by directly
minimizing infection or replication, by supporting immune system function, or
by minimizing secondary complications.
Figure 25 shows an overview of the results for curcumin
in the context of multiple COVID-19 treatments, and Figure 26 shows a plot
of efficacy vs. cost for COVID-19 treatments.
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Figure 25.
Scatter plot showing results within the context of multiple COVID-19 treatments.
Diamonds shows the results of random effects meta-analysis.
0.6% of 8,000+ proposed treatments show efficacy208.
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Figure 26. Efficacy vs. cost for COVID-19 treatments.
Curcumin is
an effective treatment for COVID-19.
Statistically significant lower risk is seen for mortality, ventilation, hospitalization, progression, recovery, and viral clearance. 18 studies from 16 independent teams in 8 countries show significant
improvements.
Meta analysis using the most serious outcome reported shows
41% [30‑51%] lower risk. Results are similar for Randomized Controlled Trials, higher quality studies, and peer-reviewed studies.
Results are very robust — in exclusion sensitivity analysis 26 of
27 studies must be excluded to avoid finding statistically significant
efficacy in pooled analysis.
Studies typically use advanced formulations for greatly improved bioavailability.
Abbaspour-Aghdam:
RCT with 30 nanocurcumin and 30 control patients in Iran, showing lower mortality and improved recovery, without statistical significance, and improved NK cell function. 160mg nanocurcumin for 21 days.
Ahmadi:
RCT 60 outpatients in Iran, 30 treated with nano-curcumin showing lower hospitalization and faster recovery with treatment.
Ahmadi (B):
RCT 76 hospitalized patients, showing improved recovery with nanocurcumin. Authors note that pure curcumin is limited due to rapid metabolism, low bio-availability, weak aqueous solubility, and systemic deletion, and that the nanocurcumin formulation used improves curcumin’s solubility, stability, half-life, and bioavailability. The dropout rate was higher in the curcumin group, in part due to discontinuation for side effects. Authors do not provide detailed discharge criteria.
Aldwihi:
Retrospective survey-based analysis of 738 COVID-19 patients in Saudi Arabia, showing lower hospitalization with vitamin C, turmeric, zinc, and nigella sativa, and higher hospitalization with vitamin D. For vitamin D, most patients continued prophylactic use. For vitamin C, the majority of patients continued prophylactic use. For nigella sativa, the majority of patients started use during infection. Authors do not specify the fraction of prophylactic use for turmeric and zinc.
Asadirad:
RCT 60 hospitalized patients in Iran, 30 treated with nano-curcumin, showing significant improvements in inflammatory cytokines, and improvements in clinical outcomes without statistical significance. 240 mg/day nano-curcumin for 7 days.
Askari:
Small RCT 46 outpatients in Iran, 23 treated with curcimin-piperine, showing no significant difference in recovery. 1000mg curcumin and 10mg piperine/day for 14 days.
Bejan:
Retrospective 9,748 COVID-19 patients in the USA showing lower hospitalization with turmeric extract.
Chitre:
RCT 208 moderate COVID-19 patients in India, 103 treated with a combination of turmeric, ashwagandha, boswellia, and ginger, showing improved recovery with treatment. The dose of curcumin is unknown and bioavailability may be poor.
Din Ujjan:
Small RCT with 50 outpatients, 25 treated with curcumin, quercetin, and vitamin D, showing improved recovery and viral clearance with treatment. 168mg curcumin, 260mg, 360IU vitamin D3 daily for 14 days.
Gérain:
RCT 49 hospitalized COVID-19 patients, 25 treated with curcumin and quercetin, shower lower mortality/ICU admission and improved recovery with treatment. All patients received vitamin D.
336mg curcumin, 520mg quercetin, and 18μg vitamin D3 daily for 14 days. The control arm received 20μg vitamin D3 daily. Baseline fever favored treatment while vaccination favored control.
336mg curcumin, 520mg quercetin, and 18μg vitamin D3 daily for 14 days. The control arm received 20μg vitamin D3 daily. Baseline fever favored treatment while vaccination favored control.
Hartono:
RCT with 30 patients treated with curcumin and virgin coconut oil (VCO), and 30 SOC patients in Indonesia, showing faster viral clearance with treatment. Treatment also reduced IL-1β, IL-2, IL-6, IL-18, and IFN-β levels. VCO improves the bioavailability of curcumin. There were large unadjusted differences in baseline severity and age, for example 20% vs. 47% of patients >50. VCO 30ml and curcumin 1g tid for 21 days. 066/UN27.06.6.1/KEPK/EC/2020.
Hassaniazad:
Small RCT with 40 low risk patients in Iran, 20 treated with nano-curcumin, showing no significant difference in outcomes with treatment. Authors note that treatment can improve peripheral blood inflammatory indices and modulate immune response by decreasing Th1 and Th17 responses, increasing T regulatory responses, further reducing IL-17 and IFN-γ, and increasing suppressive cytokines TGF-β and IL-4.
Hellou:
RCT 50 hospitalized patients in Israel, 33 treated with curcumin, vitamin C, artemisinin, and frankincense oral spray, showing improved recovery with treatment.
Kartika:
Retrospective 246 hospitalized patients in Indonesia, 136 treated with curcumin, showing shorter hospitalization time with treatment. All patients received vitamin C, D, and zinc.
Khan (B):
RCT 50 COVID+ outpatients in Pakistan, 25 treated with curcumin, quercetin, and vitamin D, showing significantly faster viral clearance, significantly improved CRP, and faster resolution of acute symptoms (p=0.154). 168mg curcumin, 260mg quercetin and 360IU cholecalciferol.
Kishimoto:
RCT 138 COVID-19 outpatients in Japan showing lower progression to fever and hypoxemia with curcuRouge, a highly bioavailable oral curcumin formulation, compared to placebo. The curcuRouge group also had a greater reduction in body temperature and took fewer antipyretic medications. The event rate was lower than expected and the difference in progression was not statistically significant.
Majeed:
RCT 100 patients in India, 50 treated with ImmuActive (curcumin, andrographolides, resveratrol, zinc, selenium, and piperine), showing improved recovery with treatment.
Nimer:
Survey 2,148 COVID-19 recovered patients in Jordan, showing lower hospitalization with turmeric prophylaxis, not reaching statistical significance.
Pawar:
RCT 140 patients, 70 treated with curcumin and piperine (for absorption), and 70 treated with probiotics, showing faster recovery, lower progression, and lower mortality with curcumin.
Saber-Moghaddam:
Small prospective nonrandomized trial with 41 patients, 21 treated with curcumin, showing lower disease progression and faster recovery with treatment. IRCT20200408046990N1.
Sadeghizadeh:
RCT 42 hospitalized moderate/severe COVID-19 patients in Iran, showing lower progression and improved recovery with nano-curcumin. Nano-curcumin 70mg bid for 14 days.
Sankhe:
RCT 174 patients in India, 87 treated with AyurCoro-3 (turmeric, gomutra, potassium alum, khadisakhar, bos indicus milk, ghee), showing faster recovery with treatment. EC/NEW/INST/2019/245.
Sankhe (B):
RCT with 60 hospitalized patients treated with Ayurcov and 60 control patients in India, showing improved viral clearance and faster symptom resolution in the mild/moderate group, but no significant differences in the severe group. Ayurcov contains curcuma longa, go ark, sphatika (alum), sita (rock candy), godugdham (bos indicus) milk, and goghritam (bos indicus ghee).
Shehab:
Retrospective survey-based analysis of 349 COVID-19 patients, showing a lower risk of severe cases with vitamin D, zinc, turmeric, and honey prophylaxis in unadjusted analysis, without statistical significance. REC/UG/2020/03.
Tahmasebi:
RCT 40 hospitalized, 40 ICU, and 40 control patients in Iran, showing lower mortality and improved regulatory T cell responses with nanocurcumin treatment (SinaCurcumin).
Thomas:
RCT 147 long COVID patients in the UK, 56 treated with a phytochemical-rich concentrated food capsule, showing improved recovery with treatment. Treatment included curcumin, bioflavonoids, chamomile, ellagic acid, and resveratrol.
Valizadeh:
Small RCT with 40 nano-curcumin patients and 40 control patients showing lower mortality with treatment. Authors conclude that nano-curcumin may be able to modulate the increased rate of inflammatory cytokines especially IL-1β and IL-6 mRNA expression and cytokine secretion in COVID-19 patients, which may improve clinical outcomes.
We perform ongoing searches of PubMed, medRxiv, Europe PMC,
ClinicalTrials.gov, The Cochrane Library, Google Scholar, Research
Square, ScienceDirect, Oxford University Press, the reference lists of other
studies and meta-analyses, and submissions to the site c19early.org.
Search terms are curcumin and COVID-19 or SARS-CoV-2. Automated searches are performed twice daily, with all matches reviewed for inclusion.
All studies regarding the use of curcumin for COVID-19 that report
a comparison with a control group are included in the main analysis.
Sensitivity analysis is performed, excluding studies with major issues,
epidemiological studies, and studies with minimal available information.
This is a living analysis and is updated regularly.
We extracted effect sizes and associated data from all studies.
If studies report multiple kinds of effects then the most serious
outcome is used in pooled analysis, while other outcomes are included in the
outcome specific analyses. For example, if effects for mortality and cases are
both reported, the effect for mortality is used, this may be different to the
effect that a study focused on.
If symptomatic
results are reported at multiple times, we used the latest time, for example
if mortality results are provided at 14 days and 28 days, the results at 28
days have preference. Mortality alone is preferred over combined outcomes.
Outcomes with zero events in both arms are not used, the next most serious
outcome with one or more events is used. For example, in low-risk populations
with no mortality, a reduction in mortality with treatment is not possible,
however a reduction in hospitalization, for example, is still valuable.
Clinical outcomes are considered more important than viral test status. When
basically all patients recover in both treatment and control groups,
preference for viral clearance and recovery is given to results mid-recovery
where available. After most or all patients have recovered there is little or
no room for an effective treatment to do better, however faster recovery is
valuable.
If only individual symptom data is available, the most serious symptom has
priority, for example difficulty breathing or low SpO2 is more
important than cough.
When results provide an odds ratio, we compute the relative risk when
possible, or convert to a relative risk according to234.
Reported confidence intervals and p-values were used when available,
using adjusted values when provided. If multiple types of adjustments are
reported propensity score matching and multivariable regression has preference
over propensity score matching or weighting, which has preference over
multivariable regression. Adjusted results have preference over unadjusted
results for a more serious outcome when the adjustments significantly alter
results. When needed, conversion between reported p-values and
confidence intervals followed Altman, Altman (B), and Fisher's exact
test was used to calculate p-values for event data. If continuity
correction for zero values is required, we use the reciprocal of the opposite
arm with the sum of the correction factors equal to 1237.
Results are expressed with RR < 1.0 favoring treatment, and using the risk of
a negative outcome when applicable (for example, the risk of death rather than
the risk of survival). If studies only report relative continuous values such
as relative times, the ratio of the time for the treatment group versus the
time for the control group is used. Calculations are done in Python
(3.13.0) with
scipy (1.14.1), pythonmeta (1.26), numpy (1.26.4), statsmodels (0.14.4), and plotly (5.24.1).
Forest plots are computed using PythonMeta238
with the DerSimonian and Laird random effects model (the fixed effect
assumption is not plausible in this case) and inverse variance weighting.
Results are presented with 95% confidence intervals. Heterogeneity among studies was
assessed using the I2 statistic.
Mixed-effects meta-regression results are computed with R (4.4.0) using the metafor
(4.6-0) and rms (6.8-0) packages, and using the most serious sufficiently powered outcome.
For all statistical tests, a p-value less than 0.05 was considered statistically significant.
Grobid 0.8.0 is used to parse PDF documents.
We have classified studies as early treatment if most patients
are not already at a severe stage at the time of treatment (for example based
on oxygen status or lung involvement), and treatment started within 5 days of
the onset of symptoms. If studies contain a mix of early treatment and late
treatment patients, we consider the treatment time of patients contributing
most to the events (for example, consider a study where most patients are
treated early but late treatment patients are included, and all mortality
events were observed with late treatment patients).
We note that a shorter time may be preferable. Antivirals are typically only
considered effective when used within a shorter timeframe, for example 0-36 or
0-48 hours for oseltamivir, with longer delays not being effective91,92.
We received no funding, this research is done in our spare
time. We have no affiliations with any pharmaceutical companies or political
parties.
A summary of study results is below. Please submit
updates and corrections at https://c19early.org/tmeta.html.
Effect extraction follows pre-specified rules as detailed above
and gives priority to more serious outcomes.
For pooled analyses, the first (most serious) outcome is used, which may
differ from the effect a paper focuses on.
Other outcomes are used in outcome specific analyses.
| Ahmadi, 6/19/2021, Double Blind Randomized Controlled Trial, Iran, peer-reviewed, 11 authors, study period April 2020 - July 2020. | risk of hospitalization, 85.7% lower, RR 0.14, p = 0.24, treatment 0 of 30 (0.0%), control 3 of 30 (10.0%), NNT 10.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| recovery time, 20.6% lower, relative time 0.79, p = 0.37, treatment 30, control 30. | |
| Aldwihi, 5/11/2021, retrospective, Saudi Arabia, peer-reviewed, survey, mean age 36.5, 8 authors, study period August 2020 - October 2020. | risk of hospitalization, 31.2% lower, RR 0.69, p = 0.10, treatment 30 of 144 (20.8%), control 207 of 594 (34.8%), NNT 7.1, adjusted per study, odds ratio converted to relative risk, multivariable. |
| Askari, 6/6/2022, Double Blind Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 11 authors, study period November 2020 - April 2021, trial IRCT20121216011763N46. | risk of no recovery, 26.5% lower, RR 0.74, p = 0.26, treatment 13, control 13, all symptoms combined. |
| risk of no recovery, 125.0% higher, RR 2.25, p = 0.58, treatment 3 of 8 (37.5%), control 1 of 6 (16.7%), dyspnea. | |
| risk of no recovery, 433.3% higher, RR 5.33, p = 0.19, treatment 2 of 6 (33.3%), control 0 of 7 (0.0%), continuity correction due to zero event (with reciprocal of the contrasting arm), ague. | |
| risk of no recovery, 72.9% lower, RR 0.27, p = 0.04, treatment 2 of 12 (16.7%), control 8 of 13 (61.5%), NNT 2.2, weakness. | |
| risk of no recovery, 40.0% lower, RR 0.60, p = 0.42, treatment 3 of 10 (30.0%), control 7 of 14 (50.0%), NNT 5.0, muscular pain. | |
| risk of no recovery, 38.5% lower, RR 0.62, p = 0.65, treatment 4 of 13 (30.8%), control 4 of 8 (50.0%), NNT 5.2, headache. | |
| risk of no recovery, 71.4% higher, RR 1.71, p = 1.00, treatment 2 of 7 (28.6%), control 1 of 6 (16.7%), sore throat. | |
| risk of no recovery, 12.5% lower, RR 0.88, p = 1.00, treatment 1 of 8 (12.5%), control 1 of 7 (14.3%), NNT 56, sputum cough. | |
| risk of no recovery, no change, RR 1.00, p = 1.00, treatment 3 of 13 (23.1%), control 3 of 13 (23.1%), dry cough. | |
| Chitre, 11/23/2022, Double Blind Randomized Controlled Trial, placebo-controlled, India, peer-reviewed, 8 authors, study period September 2020 - April 2021, this trial uses multiple treatments in the treatment arm (combined with ashwagandha, boswellia, ginger) - results of individual treatments may vary, trial CTRI/2020/09/027817. | recovery time, 11.3% lower, relative time 0.89, p = 0.04, treatment 89, control 86. |
| fever, 11.0% lower, RR 0.89, p = 0.03, treatment 70 of 89 (78.7%), control 76 of 86 (88.4%), NNT 10, day 4. | |
| congestion, 20.0% lower, RR 0.80, p = 0.05, treatment 89, control 86, mid-recovery, day 7. | |
| sore throat, 20.0% lower, RR 0.80, p = 0.09, treatment 89, control 86, mid-recovery, day 7. | |
| cough, 14.3% lower, RR 0.86, p = 0.14, treatment 89, control 86, mid-recovery, day 7. | |
| dyspnea, 15.4% lower, RR 0.85, p = 0.15, treatment 89, control 86, mid-recovery, day 7. | |
| pain, 8.3% lower, RR 0.92, p = 0.41, treatment 89, control 86, mid-recovery, day 7. | |
| fatigue, 16.7% lower, RR 0.83, p = 0.13, treatment 89, control 86, mid-recovery, day 7. | |
| headache, 16.7% lower, RR 0.83, p = 0.12, treatment 89, control 86, mid-recovery, day 7. | |
| chills, 18.2% lower, RR 0.82, p = 0.09, treatment 89, control 86, mid-recovery, day 7. | |
| diarrhea, 25.0% lower, RR 0.75, p = 0.08, treatment 89, control 86, mid-recovery, day 7. | |
| vomiting, 18.2% lower, RR 0.82, p = 0.07, treatment 89, control 86, mid-recovery, day 7. | |
| smell, 16.7% lower, RR 0.83, p = 0.06, treatment 89, control 86, mid-recovery, day 7. | |
| taste, 16.7% lower, RR 0.83, p = 0.14, treatment 89, control 86, mid-recovery, day 7. | |
| Din Ujjan, 1/18/2023, Randomized Controlled Trial, Pakistan, peer-reviewed, 6 authors, study period 21 September, 2021 - 21 January, 2022, this trial uses multiple treatments in the treatment arm (combined with quercetin and vitamin D) - results of individual treatments may vary, trial NCT04603690 (history). | risk of no recovery, 28.6% lower, RR 0.71, p = 0.11, treatment 15 of 25 (60.0%), control 21 of 25 (84.0%), NNT 4.2, no symptoms, day 7. |
| risk of no recovery, 71.4% lower, RR 0.29, p < 0.001, treatment 6 of 25 (24.0%), control 21 of 25 (84.0%), NNT 1.7, <= 1 symptom, day 7. | |
| risk of no recovery, 76.9% lower, RR 0.23, p = 0.005, treatment 3 of 25 (12.0%), control 13 of 25 (52.0%), NNT 2.5, <= 2 symptoms, day 7. | |
| risk of no recovery, 85.7% lower, RR 0.14, p = 0.23, treatment 0 of 25 (0.0%), control 3 of 25 (12.0%), NNT 8.3, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), <= 3 symptoms, day 7. | |
| risk of no viral clearance, 90.9% lower, RR 0.09, p = 0.05, treatment 0 of 25 (0.0%), control 5 of 25 (20.0%), NNT 5.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 14. | |
| risk of no viral clearance, 73.7% lower, RR 0.26, p < 0.001, treatment 5 of 25 (20.0%), control 19 of 25 (76.0%), NNT 1.8, day 7. | |
| Khan (B), 5/1/2022, Randomized Controlled Trial, Pakistan, peer-reviewed, 7 authors, study period 2 September, 2021 - 28 November, 2021, this trial uses multiple treatments in the treatment arm (combined with quercetin and vitamin D) - results of individual treatments may vary, trial NCT05130671 (history). | risk of no recovery, 33.3% lower, RR 0.67, p = 0.15, treatment 10 of 25 (40.0%), control 15 of 25 (60.0%), NNT 5.0. |
| relative CRP reduction, 39.1% better, RR 0.61, p = 0.006, treatment 25, control 25. | |
| risk of no viral clearance, 50.0% lower, RR 0.50, p = 0.009, treatment 10 of 25 (40.0%), control 20 of 25 (80.0%), NNT 2.5. | |
| Kishimoto, 6/24/2024, Double Blind Randomized Controlled Trial, placebo-controlled, Japan, peer-reviewed, 15 authors, study period February 2022 - January 2023, trial jRCTs051210176. | SpO2<96 or temperature≥37.5, 46.8% lower, HR 0.53, p = 0.48, treatment 2 of 71 (2.8%), control 4 of 67 (6.0%), NNT 32, Cox proportional hazards. |
| Majeed, 10/11/2021, Double Blind Randomized Controlled Trial, India, peer-reviewed, 4 authors, study period September 2020 - November 2020, this trial uses multiple treatments in the treatment arm (combined with andrographolides, resveratrol, zinc, selenium, and piperine) - results of individual treatments may vary, trial CTRI/2020/09/027841. | risk of mechanical ventilation, 66.2% lower, RR 0.34, p = 1.00, treatment 0 of 45 (0.0%), control 1 of 47 (2.1%), NNT 47, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| risk of hospitalization, 79.7% lower, RR 0.20, p = 0.49, treatment 0 of 45 (0.0%), control 2 of 47 (4.3%), NNT 24, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). | |
| relative ordinal scale, 43.0% better, RR 0.57, p = 0.004, treatment 45, control 47, day 28. | |
| risk of no recovery, 24.6% lower, RR 0.75, p = 0.08, treatment 26 of 45 (57.8%), control 36 of 47 (76.6%), NNT 5.3, day 28. | |
| time to viral-, 5.8% lower, relative time 0.94, p = 0.47, treatment 45, control 47. | |
| Pawar, 5/28/2021, Double Blind Randomized Controlled Trial, India, peer-reviewed, 8 authors, study period July 2020 - September 2020, this trial compares with another treatment - results may be better when compared to placebo, trial CTRI/2020/05/025482. | risk of death, 81.8% lower, RR 0.18, p = 0.02, treatment 2 of 70 (2.9%), control 11 of 70 (15.7%), NNT 7.8. |
| risk of death, 60.0% lower, RR 0.40, p = 0.39, treatment 2 of 15 (13.3%), control 5 of 15 (33.3%), NNT 5.0, severe group. | |
| risk of death, 90.9% lower, RR 0.09, p = 0.05, treatment 0 of 25 (0.0%), control 5 of 25 (20.0%), NNT 5.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), moderate group. | |
| risk of death, 66.7% lower, RR 0.33, p = 1.00, treatment 0 of 30 (0.0%), control 1 of 30 (3.3%), NNT 30, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), mild group. | |
| Saber-Moghaddam, 1/3/2021, prospective, Iran, peer-reviewed, 9 authors. | risk of progression, 94.3% lower, RR 0.06, p = 0.001, treatment 0 of 21 (0.0%), control 8 of 20 (40.0%), NNT 2.5, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| risk of no recovery, 38.4% lower, RR 0.62, p = 0.04, treatment 11 of 21 (52.4%), control 17 of 20 (85.0%), NNT 3.1. | |
| hospitalization time, 44.8% lower, relative time 0.55, p < 0.001, treatment 21, control 20. | |
| Sankhe, 8/10/2021, Randomized Controlled Trial, India, peer-reviewed, 8 authors, study period October 2020 - March 2021, this trial uses multiple treatments in the treatment arm (combined with gomutra, potassium alum, khadisakhar, bos indicus milk, ghee) - results of individual treatments may vary. | risk of death, 88.9% lower, RR 0.11, p = 0.12, treatment 0 of 87 (0.0%), control 4 of 87 (4.6%), NNT 22, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| risk of mechanical ventilation, 75.0% lower, RR 0.25, p = 0.37, treatment 1 of 87 (1.1%), control 4 of 87 (4.6%), NNT 29. | |
| risk of no 2-point improvement, 46.5% lower, RR 0.54, p = 0.002, treatment 29 of 87 (33.3%), control 60 of 87 (69.0%), NNT 2.8, inverted to make RR<1 favor treatment, odds ratio converted to relative risk, day 7 mid-recovery. | |
| hospitalization time, 10.0% lower, relative time 0.90, p = 0.40, treatment 87, control 87. |
Effect extraction follows pre-specified rules as detailed above
and gives priority to more serious outcomes.
For pooled analyses, the first (most serious) outcome is used, which may
differ from the effect a paper focuses on.
Other outcomes are used in outcome specific analyses.
| Abbaspour-Aghdam, 9/17/2022, Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 16 authors, trial IRCT20200324046851N1. | risk of death, 71.4% lower, RR 0.29, p = 0.15, treatment 2 of 30 (6.7%), control 7 of 30 (23.3%), NNT 6.0. |
| risk of no recovery, 86.3% lower, RR 0.14, p = 0.04, treatment 1 of 28 (3.6%), control 6 of 23 (26.1%), NNT 4.4, dyspnea. | |
| risk of no recovery, 89.9% lower, RR 0.10, p = 0.04, treatment 0 of 28 (0.0%), control 4 of 23 (17.4%), NNT 5.8, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), fever >39.0. | |
| risk of no recovery, 38.4% lower, RR 0.62, p = 0.17, treatment 9 of 28 (32.1%), control 12 of 23 (52.2%), NNT 5.0, bilateral chest radiograph involvement. | |
| risk of no recovery, 58.9% lower, RR 0.41, p = 0.27, treatment 3 of 28 (10.7%), control 6 of 23 (26.1%), NNT 6.5, cough. | |
| risk of no recovery, 81.6% lower, RR 0.18, p = 0.20, treatment 0 of 28 (0.0%), control 2 of 23 (8.7%), NNT 12, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), headache. | |
| Ahmadi (B), 7/28/2023, Double Blind Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 5 authors, study period December 2021 - March 2022, trial IRCT20211126053183N1. | risk of oxygen therapy, 58.0% lower, RR 0.42, p = 0.06, treatment 5 of 29 (17.2%), control 16 of 39 (41.0%), NNT 4.2. |
| relative improvement in SpO2, 67.2% better, RR 0.33, p = 0.04, treatment mean 3.32 (±3.84) n=29, control mean 1.09 (±4.71) n=39. | |
| risk of no recovery, 49.6% lower, RR 0.50, p = 0.33, treatment 3 of 29 (10.3%), control 8 of 39 (20.5%), NNT 9.8, chest pain. | |
| risk of no recovery, 34.5% higher, RR 1.34, p = 1.00, treatment 1 of 29 (3.4%), control 1 of 39 (2.6%), chills. | |
| risk of no recovery, 58.0% lower, RR 0.42, p = 0.06, treatment 5 of 29 (17.2%), control 16 of 39 (41.0%), NNT 4.2, cough. | |
| risk of no recovery, 77.7% lower, RR 0.22, p = 0.50, treatment 0 of 29 (0.0%), control 2 of 39 (5.1%), NNT 20, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), sore throat. | |
| risk of no recovery, 63.8% lower, RR 0.36, p < 0.001, treatment 7 of 29 (24.1%), control 26 of 39 (66.7%), NNT 2.4, fatigue. | |
| risk of no recovery, 91.3% lower, RR 0.09, p = 0.03, treatment 0 of 29 (0.0%), control 6 of 39 (15.4%), NNT 6.5, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), myalgia. | |
| risk of no recovery, 8.9% higher, RR 1.09, p = 0.81, treatment 17 of 29 (58.6%), control 21 of 39 (53.8%), anosmia. | |
| risk of no recovery, 10.3% lower, RR 0.90, p = 1.00, treatment 8 of 29 (27.6%), control 12 of 39 (30.8%), NNT 31, ageusia. | |
| risk of no recovery, 10.3% lower, RR 0.90, p = 1.00, treatment 2 of 29 (6.9%), control 3 of 39 (7.7%), NNT 126, anorexia. | |
| risk of no recovery, 63.6% lower, RR 0.36, p = 1.00, treatment 0 of 29 (0.0%), control 1 of 39 (2.6%), NNT 39, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), diarrhea. | |
| risk of no recovery, 234.5% higher, RR 3.34, p = 0.43, treatment 1 of 29 (3.4%), control 0 of 39 (0.0%), continuity correction due to zero event (with reciprocal of the contrasting arm), nausea. | |
| Asadirad, 1/17/2022, Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 7 authors, study period June 2020 - July 2020. | risk of death, 25.9% lower, RR 0.74, p = 0.74, treatment 5 of 27 (18.5%), control 6 of 24 (25.0%), NNT 15, excluding patients that stopped treatment due to progression - 3 for curcumin and 6 for control. |
| risk of progression, 50.0% lower, RR 0.50, p = 0.47, treatment 3 of 30 (10.0%), control 6 of 30 (20.0%), NNT 10.0. | |
| risk of unresolved fever, 45.3% lower, RR 0.55, p = 0.09, treatment 8 of 27 (29.6%), control 13 of 24 (54.2%), NNT 4.1. | |
| risk of unresolved dyspnea, 28.9% lower, RR 0.71, p = 0.72, treatment 4 of 27 (14.8%), control 5 of 24 (20.8%), NNT 17. | |
| risk of unresolved cough, 40.7% lower, RR 0.59, p = 0.36, treatment 6 of 27 (22.2%), control 9 of 24 (37.5%), NNT 6.5. | |
| risk of O2 <92%, 36.5% lower, RR 0.63, p = 0.51, treatment 5 of 27 (18.5%), control 7 of 24 (29.2%), NNT 9.4. | |
| risk of O2 <97%, 20.0% lower, RR 0.80, p = 0.21, treatment 18 of 27 (66.7%), control 20 of 24 (83.3%), NNT 6.0. | |
| Gérain, 6/22/2023, Randomized Controlled Trial, Belgium, peer-reviewed, 8 authors, study period 1 April, 2021 - 29 October, 2021, this trial uses multiple treatments in the treatment arm (combined with quercetin) - results of individual treatments may vary, trial NCT04844658 (history). | risk of death, 67.1% lower, RR 0.33, p = 0.49, treatment 0 of 25 (0.0%), control 1 of 24 (4.2%), NNT 24, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 7. |
| risk of death/ICU, 91.1% lower, RR 0.09, p = 0.02, treatment 0 of 25 (0.0%), control 5 of 24 (20.8%), NNT 4.8, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 7. | |
| risk of mechanical ventilation, 89.1% lower, RR 0.11, p = 0.05, treatment 0 of 25 (0.0%), control 4 of 24 (16.7%), NNT 6.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 7. | |
| risk of ICU admission, 89.1% lower, RR 0.11, p = 0.05, treatment 0 of 25 (0.0%), control 4 of 24 (16.7%), NNT 6.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 7. | |
| risk of no hospital discharge, 72.6% lower, RR 0.27, p = 0.07, treatment 2 of 25 (8.0%), control 7 of 24 (29.2%), NNT 4.7, day 14. | |
| risk of no hospital discharge, 58.9% lower, RR 0.41, p = 0.02, treatment 6 of 25 (24.0%), control 14 of 24 (58.3%), NNT 2.9, day 7. | |
| hospitalization time, 37.5% lower, relative time 0.62, p = 0.008, treatment median 5.0 IQR 4.0 n=25, control median 8.0 IQR 6.0 n=24. | |
| relative WHO score, 50.0% better, RR 0.50, p = 0.04, treatment 22, control 24, day 7. | |
| Hartono, 2/22/2022, Randomized Controlled Trial, Indonesia, peer-reviewed, 13 authors, study period May 2020 - September 2020, this trial uses multiple treatments in the treatment arm (combined with virgin coconut oil) - results of individual treatments may vary, excluded in exclusion analyses: randomization resulted in significant baseline differences that were not adjusted for. | risk of no viral clearance, 53.3% lower, RR 0.47, p < 0.001, treatment 14 of 30 (46.7%), control 30 of 30 (100.0%), NNT 1.9, day 10. |
| risk of no viral clearance, 75.0% lower, RR 0.25, p = 0.002, treatment 4 of 30 (13.3%), control 16 of 30 (53.3%), NNT 2.5, day 14. | |
| risk of no viral clearance, 66.7% lower, RR 0.33, p = 1.00, treatment 0 of 30 (0.0%), control 1 of 30 (3.3%), NNT 30, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 21. | |
| Hassaniazad, 9/19/2021, Double Blind Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 12 authors. | relative improvement in SpO2, 45.7% worse, RR 1.46, p = 0.90, treatment 20, control 20. |
| Hellou, 5/19/2022, Double Blind Randomized Controlled Trial, placebo-controlled, Israel, peer-reviewed, 6 authors, study period 8 May, 2020 - 21 December, 2020, this trial uses multiple treatments in the treatment arm (combined with vitamin C, artemisinin, and frankincense) - results of individual treatments may vary, trial NCT04382040 (history). | relative NEWS2 score, 76.7% better, RR 0.23, p = 0.04, treatment mean 0.52 (±0.67) n=33, control mean 2.23 (±3.2) n=17, day 15. |
| risk of oxygen therapy, 92.2% lower, RR 0.08, p = 0.01, treatment 0 of 33 (0.0%), control 4 of 17 (23.5%), NNT 4.2, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 15. | |
| oxygen time, 69.7% lower, relative time 0.30, p = 0.17, treatment mean 2.3 (±1.4) n=33, control mean 7.6 (±4.6) n=17. | |
| hospitalization time, 13.3% lower, relative time 0.87, p = 0.92, treatment mean 7.8 (±7.3) n=33, control mean 9.0 (±8.0) n=17. | |
| risk of no viral clearance, 9.8% lower, RR 0.90, p = 0.77, treatment 14 of 33 (42.4%), control 8 of 17 (47.1%), NNT 22, day 15. | |
| Kartika, 1/28/2022, retrospective, Indonesia, preprint, 6 authors, study period January 2021 - June 2021. | hospitalization time, 41.0% lower, relative time 0.59, p = 0.048, treatment 139, control 107. |
| Sadeghizadeh, 4/29/2023, Double Blind Randomized Controlled Trial, placebo-controlled, Iran, peer-reviewed, 12 authors, trial IRCT20170128032241N3. | risk of progression, 92.3% lower, RR 0.08, p = 0.02, treatment 0 of 21 (0.0%), control 6 of 21 (28.6%), NNT 3.5, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| hospitalization time, 24.5% lower, relative time 0.75, p = 0.007, treatment mean 7.7 (±2.3) n=21, control mean 10.2 (±3.3) n=21. | |
| relative chest CT score, 67.5% better, RR 0.33, p < 0.001, treatment mean 1.3 (±0.82) n=21, control mean 4.0 (±1.8) n=21, day 14. | |
| risk of no recovery, 66.7% lower, RR 0.33, p = 0.61, treatment 1 of 21 (4.8%), control 3 of 21 (14.3%), NNT 10, day 14, dyspnea/oxygen need. | |
| risk of no recovery, 80.0% lower, RR 0.20, p = 0.18, treatment 1 of 21 (4.8%), control 5 of 21 (23.8%), NNT 5.2, day 14, fever. | |
| risk of no recovery, 85.7% lower, RR 0.14, p = 0.04, treatment 1 of 21 (4.8%), control 7 of 21 (33.3%), NNT 3.5, day 14, cough. | |
| risk of no recovery, 80.0% lower, RR 0.20, p = 0.49, treatment 0 of 21 (0.0%), control 2 of 21 (9.5%), NNT 10, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 14, headache. | |
| risk of no recovery, 75.0% lower, RR 0.25, p = 0.34, treatment 1 of 21 (4.8%), control 4 of 21 (19.0%), NNT 7.0, day 14, fatigue. | |
| risk of no recovery, 75.0% lower, RR 0.25, p = 0.34, treatment 1 of 21 (4.8%), control 4 of 21 (19.0%), NNT 7.0, day 14, myalgia. | |
| risk of no recovery, 66.7% lower, RR 0.33, p = 1.00, treatment 0 of 21 (0.0%), control 1 of 21 (4.8%), NNT 21, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 14, diarrhea. | |
| risk of no recovery, 50.0% lower, RR 0.50, p = 1.00, treatment 1 of 21 (4.8%), control 2 of 21 (9.5%), NNT 21, day 14, inappetence. | |
| risk of no recovery, 66.7% lower, RR 0.33, p = 1.00, treatment 0 of 21 (0.0%), control 1 of 21 (4.8%), NNT 21, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 14, nausea. | |
| Sankhe (B), 3/25/2022, Single Blind Randomized Controlled Trial, India, peer-reviewed, 10 authors, study period June 2020 - November 2020, this trial uses multiple treatments in the treatment arm (combined with gomutra, potassium alum, khadisakhar, bos indicus milk, ghee) - results of individual treatments may vary. | risk of death, 85.7% lower, RR 0.14, p = 0.24, treatment 0 of 60 (0.0%), control 3 of 60 (5.0%), NNT 20, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| risk of mechanical ventilation, 85.7% lower, RR 0.14, p = 0.24, treatment 0 of 60 (0.0%), control 3 of 60 (5.0%), NNT 20, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). | |
| risk of ICU admission, 66.7% lower, RR 0.33, p = 0.62, treatment 1 of 60 (1.7%), control 3 of 60 (5.0%), NNT 30. | |
| hospitalization time, 10.0% lower, relative time 0.90, p = 0.40, treatment 45, control 45, moderate group. | |
| hospitalization time, 16.7% lower, relative time 0.83, p = 0.20, treatment 15, control 15, severe group. | |
| recovery time, 31.9% lower, relative time 0.68, p < 0.001, treatment 45, control 45, moderate group, fever. | |
| recovery time, 36.1% lower, relative time 0.64, p < 0.001, treatment 45, control 45, moderate group, dyspnea. | |
| recovery time, 4.3% lower, relative time 0.96, p = 0.74, treatment 15, control 15, severe group, fever. | |
| recovery time, 4.8% higher, relative time 1.05, p = 0.10, treatment 15, control 15, severe group, dyspnea. | |
| relative Ct increase, 44.4% better, RR 0.56, p = 0.003, treatment mean 9.98 (±6.39) n=44, control mean 5.55 (±6.91) n=43, moderate group. | |
| Tahmasebi, 3/28/2021, Double Blind Randomized Controlled Trial, Iran, peer-reviewed, 14 authors. | risk of death, 83.3% lower, RR 0.17, p = 0.11, treatment 1 of 40 (2.5%), control 6 of 40 (15.0%), NNT 8.0. |
| risk of death, 66.7% lower, RR 0.33, p = 1.00, treatment 0 of 20 (0.0%), control 1 of 20 (5.0%), NNT 20, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), non-ICU patients. | |
| risk of death, 80.0% lower, RR 0.20, p = 0.18, treatment 1 of 20 (5.0%), control 5 of 20 (25.0%), NNT 5.0, ICU patients. | |
| Thomas, 3/22/2022, Double Blind Randomized Controlled Trial, placebo-controlled, United Kingdom, peer-reviewed, 7 authors, study period May 2020 - May 2021, this trial uses multiple treatments in the treatment arm (combined with bioflavonoids, chamomile, ellagic acid, resveratrol) - results of individual treatments may vary, Phyto-V trial. | relative improvement, 44.3% better, RR 0.56, p = 0.02, treatment mean 6.1 (±7.5) n=74, control mean 3.4 (±6.1) n=73, CFS. |
| relative improvement, 81.8% better, RR 0.18, p < 0.001, treatment mean 6.6 (±10.5) n=74, control mean 1.2 (±7.4) n=73, SWS. | |
| relative improvement, 63.6% better, RR 0.36, p = 0.02, treatment mean 1.1 (±2.0) n=74, control mean 0.4 (±1.5) n=73, CSS. | |
| Valizadeh, 10/20/2020, Double Blind Randomized Controlled Trial, Iran, peer-reviewed, 12 authors. | risk of death, 50.0% lower, RR 0.50, p = 0.30, treatment 4 of 20 (20.0%), control 8 of 20 (40.0%), NNT 5.0. |
Effect extraction follows pre-specified rules as detailed above
and gives priority to more serious outcomes.
For pooled analyses, the first (most serious) outcome is used, which may
differ from the effect a paper focuses on.
Other outcomes are used in outcome specific analyses.
| Bejan, 2/28/2021, retrospective, USA, peer-reviewed, mean age 42.0, 6 authors. | risk of hospitalization, 59.0% lower, OR 0.41, p = 0.048, treatment 148, control 9,600, adjusted per study, RR approximated with OR. |
| Nimer, 6/10/2022, retrospective, Jordan, peer-reviewed, survey, mean age 40.2, 4 authors, study period March 2021 - July 2021. | risk of hospitalization, 30.8% lower, RR 0.69, p = 0.08, treatment 29 of 329 (8.8%), control 179 of 1,819 (9.8%), adjusted per study, odds ratio converted to relative risk, multivariable. |
| risk of severe case, 12.6% lower, RR 0.87, p = 0.47, treatment 40 of 329 (12.2%), control 211 of 1,819 (11.6%), adjusted per study, odds ratio converted to relative risk, multivariable. | |
| Shehab, 2/28/2022, retrospective, multiple countries, peer-reviewed, survey, 7 authors, study period September 2020 - March 2021, excluded in exclusion analyses: unadjusted results with no group details. | risk of severe case, 42.4% lower, RR 0.58, p = 0.55, treatment 2 of 32 (6.2%), control 24 of 221 (10.9%), NNT 22, unadjusted, severe vs. mild cases. |
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