Nigella Sativa reduces COVID-19 risk: real-time meta analysis of 14 studies
Control
Abstract
Significantly lower risk is seen for ventilation, hospitalization, recovery, cases, and viral clearance. 11 studies from 10 independent teams in 8 countries show significant
benefit.
Meta analysis using the most serious outcome reported shows
43% [24‑57%] lower risk. Results are similar for Randomized Controlled Trials and higher quality studies.
Early treatment is more effective than late treatment.
Results are very robust — in exclusion sensitivity analysis 11 of
14 studies must be excluded to avoid finding statistically significant
efficacy in pooled analysis.
No treatment is 100%
effective. Protocols combine safe and effective options with individual
risk/benefit analysis and monitoring.
Dietary sources may be preferred. The quality of non-prescription supplements varies widely1-3.
All data and sources to reproduce this analysis are in the appendix.
Nigella Sativa for COVID-19 — Highlights
Studies to date suggest that Nigella Sativa reduces risk with very high confidence for hospitalization, recovery, cases, and in pooled analysis, high confidence for viral clearance, and low confidence for mortality and ventilation.
Early treatment and prophylaxis are more effective than late treatment.
12th treatment shown effective in January 2021, now with p = 0.00016 from 14 studies.
Real-time updates and corrections with a consistent protocol for 161 treatments. Outcome specific analysis and combined evidence from all studies including treatment delay, a primary confounding factor.
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 nigella sativa 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 6.4 months, compared to using all studies. Efficacy based on specific outcomes was delayed by 15.1 months, compared to using pooled outcomes. Efficacy based on specific outcomes in RCTs was delayed by 8.7 months, compared to using pooled outcomes in RCTs.
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 injury6-18 and
cognitive deficits9,14, cardiovascular
complications19-23, organ failure, and death.
Minimizing replication as early as possible is recommended.
SARS-CoV-2 infection and replication involves the complex interplay of 100+
host and viral proteins and other factorsA,24-31, providing many
therapeutic targets for which many existing compounds have known activity.
Scientists have predicted that over 9,000 compounds may
reduce COVID-19 risk32, either by
directly minimizing infection or replication, by supporting immune system
function, or by minimizing secondary complications.
We analyze all significant
controlled studies of
nigella sativa
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, 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.
Thomas investigate a novel formulation of nigella sativa that may
be more effective for COVID-19.
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 1 summarizes the results for all stages combined, for Randomized Controlled Trials, after exclusions, and for specific outcomes.
Table 2 shows results by treatment stage.
Figure 3 plots individual results by treatment stage.
Figure 4, 5, 6, 7, 8, 9, 10, and 11
show forest plots for random effects meta-analysis of
all studies with pooled effects, mortality results, ventilation, ICU admission, hospitalization, recovery, cases, and viral clearance.
| Improvement | Studies | Patients | Authors | |
|---|---|---|---|---|
| All studies | 43% [24‑57%] *** | 14 | 3,333 | 174 |
| After exclusions | 49% [30‑62%] **** | 12 | 2,930 | 163 |
| Randomized Controlled TrialsRCTs | 41% [15‑60%] ** | 10 | 1,915 | 148 |
| Mortality | 57% [-20‑85%] | 5 | 1,342 | 80 |
| ICU admissionICU | 40% [-61‑78%] | 2 | 471 | 41 |
| HospitalizationHosp. | 34% [16‑47%] *** | 5 | 1,410 | 87 |
| Recovery | 64% [34‑80%] ** | 5 | 862 | 89 |
| Cases | 51% [21‑69%] ** | 3 | 654 | 31 |
| Viral | 62% [16‑82%] * | 4 | 345 | 67 |
| RCT mortality | 57% [-20‑85%] | 5 | 1,342 | 80 |
| RCT hospitalizationRCT hosp. | 53% [8‑76%] * | 4 | 672 | 79 |
| Early treatment | Late treatment | Prophylaxis | |
|---|---|---|---|
| All studies | 46% [19‑64%] ** | 9% [-33‑38%] | 46% [15‑65%] ** |
| After exclusions | 46% [19‑64%] ** | 39% [-157‑85%] | 51% [21‑69%] ** |
| Randomized Controlled TrialsRCTs | 82% [55‑93%] *** | 9% [-33‑38%] | 35% [14‑51%] ** |
| Mortality | 87% [51‑96%] ** | 9% [-33‑38%] | |
| ICU admissionICU | 40% [-61‑78%] | ||
| HospitalizationHosp. | 25% [7‑40%] ** | 50% [-15‑78%] | |
| Recovery | 64% [24‑82%] ** | 67% [35‑83%] ** | |
| Cases | 51% [21‑69%] ** |
||
| Viral | 62% [16‑82%] * | ||
| RCT mortality | 87% [51‑96%] ** | 9% [-33‑38%] | |
| RCT hospitalizationRCT hosp. | 73% [-61‑96%] | 50% [-15‑78%] |
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.
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.
Figure 5. Random effects meta-analysis for mortality results.
Figure 6. Random effects meta-analysis for ventilation.
Figure 7. Random effects meta-analysis for ICU admission.
Figure 8. Random effects meta-analysis for hospitalization.
Figure 9. Random effects meta-analysis for recovery.
Figure 10. Random effects meta-analysis for cases.
Figure 11. Random effects meta-analysis for viral clearance.
Figure 12 shows a comparison of results for RCTs and non-RCT studies.
Random effects meta analysis of RCTs shows
41% improvement,
compared to 40% for other studies.
Figure 13, 14, and 15
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 1 and Table 2.
Figure 12. Results for RCTs and non-RCT studies.
Figure 13. 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.
Figure 14. Random effects meta-analysis for RCT mortality results.
Figure 15. 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 biases53, and
analysis of double-blind RCTs has identified extreme levels of bias54.
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 161 treatments we have analyzed,
66% 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 [0.93‑1.07]
across 161 treatments56.
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 161 treatments
we cover, showing no significant difference in the results of RCTs compared to
observational studies, RR 1.00 [0.93‑1.07]. Similar results are found for all low-cost treatments, RR
1.02 [0.93‑1.11]. High-cost treatments
show a non-significant trend towards RCTs showing greater efficacy,
RR 0.93 [0.83‑1.04].
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 see60,61.
Currently, 53 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, 58% have been confirmed in RCTs, with a mean delay of 7.8 months (66% with 8.9 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 16 shows a forest plot for random
effects meta-analysis of all studies after exclusions.
Faruq, potential data issue.
Shehab, unadjusted results with no group details.
Figure 16. 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 hours64,65. 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 cases66 |
| <24 hours | -33 hours symptoms67 |
| 24-48 hours | -13 hours symptoms67 |
| Inpatients | -2.5 hours to improvement68 |
Figure 17 shows a mixed-effects meta-regression for efficacy
as a function of treatment delay in COVID-19 studies from 161 treatments, showing
that efficacy declines rapidly with treatment delay. Early treatment is
critical for COVID-19.
Figure 17. Early treatment is more effective. Meta-regression showing efficacy as a function of treatment delay in COVID-19 studies from 161 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
variants70, for example the Gamma variant shows significantly
different characteristics71-74. 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 variants75,76.
Effectiveness may depend strongly on the dosage and treatment regimen.
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 pooled effects are no longer required
for nigella sativa as of May 2022. Efficacy is now known based on specific outcomes for all studies and when restricted to RCTs. Efficacy based on specific outcomes was delayed by 15.1 months compared to using pooled outcomes. Efficacy based on specific outcomes in RCTs was delayed by 8.7 months compared to using pooled outcomes in RCTs.
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.
Pooling the results of studies reporting different outcomes allows us to use
more of the available information. Logically we should, and do, use additional
information when evaluating treatments—for example dose-response and
treatment delay-response relationships provide additional evidence of efficacy
that is considered when reviewing the evidence for a treatment.
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.
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 and safer 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 161
treatments we cover confirms the validity of pooled outcome analysis for COVID-19.
Figure 18 shows that lower hospitalization is very strongly associated
with lower mortality (p < 0.000000000001).
Similarly, Figure 19 shows that improved recovery is very strongly associated
with lower mortality (p < 0.000000000001).
Considering the extremes, Singh 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 20 shows that improved viral clearance is strongly associated
with fewer serious outcomes. The association is very similar to
Singh et al., with higher confidence due to the larger number of
studies. As with Singh et al., the confidence increases
when excluding the outlier treatment, from p = 0.00000011 to p = 0.0000000048.
Figure 18. Lower hospitalization is associated with lower mortality, supporting pooled outcome analysis.
Figure 19. Improved recovery is associated with lower mortality, supporting pooled outcome analysis.
Figure 18. Improved viral clearance is associated with fewer serious outcomes, supporting pooled outcome analysis.
Currently, 53 of the treatments we analyze show statistically significant efficacy or harm, defined as ≥10% decreased risk or >0% increased risk from ≥3 studies. 90% of these have been confirmed with one or more specific outcomes, with a mean delay of 4.8 months. When restricting to RCTs only, 55% of treatments showing statistically significant efficacy/harm with pooled effects have been confirmed with one or more specific outcomes, with a mean delay of 7.3 months.
Figure 21 shows when treatments were found effective during the
pandemic. Pooled outcomes often resulted in earlier detection of efficacy.
Figure 21. 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 results97-100.
For nigella sativa, 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 22 shows a scatter plot of
results for prospective and retrospective studies.
0% of retrospective studies
report a statistically significant positive effect for
one or more outcomes, compared to
92% of prospective studies, consistent with a bias toward publishing negative results.
The median effect size for
retrospective studies is 12% improvement,
compared to 57% for prospective
studies, suggesting a potential bias towards publishing results showing lower efficacy.
Figure 22. 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 23 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 < 0.05101-108.
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 23. 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. Nigella Sativa for COVID-19
lacks this because it is an inexpensive and widely available supplement.
In contrast, most COVID-19 nigella sativa 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 nigella sativa 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 alone79-95.
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.
SARS-CoV-2 infection and replication involves a complex
interplay of 100+ host and viral proteins and other
factors24-31, providing many therapeutic
targets.
Over 9,000 compounds have been predicted to reduce COVID-19
risk32, either by directly
minimizing infection or replication, by supporting immune system function, or
by minimizing secondary complications.
Figure 24 shows an overview of the results for nigella sativa
in the context of multiple COVID-19 treatments, and Figure 25 shows a plot
of efficacy vs. cost for COVID-19 treatments.
Figure 24.
Scatter plot showing results within the context of multiple COVID-19 treatments.
Diamonds shows the results of random effects meta-analysis.
0.6% of 9,000+ proposed treatments show efficacy159.
Figure 25. Efficacy vs. cost for COVID-19 treatments.
Studies to date suggest that nigella sativa is
an effective treatment for COVID-19.
Significantly lower risk is seen for ventilation, hospitalization, recovery, cases, and viral clearance. 11 studies from 10 independent teams in 8 countries show significant
benefit.
Meta analysis using the most serious outcome reported shows
43% [24‑57%] lower risk. Results are similar for Randomized Controlled Trials and higher quality studies.
Early treatment is more effective than late treatment.
Results are very robust — in exclusion sensitivity analysis 11 of
14 studies must be excluded to avoid finding statistically significant
efficacy in pooled analysis.
Prophylaxis study with 376 mostly high-risk patients, 188 treated with nigella sativa, showing significantly lower cases with treatment. Black seeds 40mg/kg orally once daily.
Open-label RCT with 419 patients in Iraq, 160 treated with Nigella Sativa, showing lower mortality and severe cases with treatment. Black seeds 40mg/kg orally once daily for 14 days.
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.
RCT with 157 patients treated with honey and nigella sativa, and 156 control patients, showing significantly faster recovery and viral clearance.
Honey (1gm/kg/day) plus encapsulated nigella sativa seeds (80mg/kg/day) orally in 2-3 divided doses daily for up to 13 days.
Honey (1gm/kg/day) plus encapsulated nigella sativa seeds (80mg/kg/day) orally in 2-3 divided doses daily for up to 13 days.
52 patient RCT in the USA with nigella sativa component thymoquinone, showing improved recovery with treatment. There was a significantly faster decline in the total symptom burden, and a significant increase in CD8+ and helper CD4+ central memory T lymphocytes. The treatment group contained 5 more vaccinated patients and 7 more overweight patients. Authors also present in vitro results showing an inhibitory effect with five SARS-CoV-2 variants including omicron.
RCT 251 high-risk individuals in India, mostly with direct contact with COVID-19 positive patients, testing polyherbal formulations Infuza, which includes nigella sativa, and Kulzam. Both formulations showed lower risk, without statisical significance, while the best results were from the combination of both.
RCT 173 family members of COVID-19 patients, showing lower incidence of COVID-19 symptoms with nasal drops containing nigella sativa oil and olea europaea oil. One drop in each nostril twice daily for 7 days.
Open label randomized trial of 150 ICU patients in Bangladesh, showing shorter ICU stay and lower requirements for increased oxygen support including mechanical ventilation with nigella sativa treatment, but no significant difference in mortality.
The large baseline difference in convalescent plasma usage suggests an error or randomization problem.
The large baseline difference in convalescent plasma usage suggests an error or randomization problem.
Prospective study of 51 mild COVID-19 cases in Nigeria, showing faster recovery and improved viral clearance with nigella sativa oil (NSO) treatment. NSO patients received 5mL twice daily in addition to usual care (zinc, vitamin C and a multivitamin).
RCT 358 hospitalized patients in Iran, 184 receiving treatment with a combination of nigella sativa and several other herbal medicines, showing shorter hospitalization time and improved recovery with treatment. IR.TUMS.VCR.REC.1399.024.
RCT 183 mild COVID-19 outpatients in Saudi Arabia, 91 treated with Nigella Sativa, showing lower hospitalization and faster recovery with treatment. 500mg Nigella Sativa oil (MARNYS Cuminmar) twice daily for 10 days. NCT04401202.
120 patient RCT comparing vitamin D, nigella sativa, and combined vitamin D+nigella sativa, showing improved symptom recovery and viral clearance with both vitamin D and nigella sativa, and further improvements with the combination of both. All patients received vitamin C, zinc, and lactoferrin.
Small RCT 41 patients treated with nigella sativa, glycyrrhiza glabra, punica granatum, and rheum palmatum, and 41 control patients, showing shorter hospitalization with treatment.
Retrospective survey-based analysis of 349 COVID-19 patients, showing no significant difference with nigella sativa prophylaxis in unadjusted analysis. REC/UG/2020/03.
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 nigella sativa 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 nigella sativa 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 to160.
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 1163.
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
(3.13.3) with
scipy (1.15.3), pythonmeta (1.26), numpy (2.2.6), statsmodels (0.14.4), and plotly (6.0.1).
Forest plots are computed using PythonMeta164
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 0.8.2 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 effective64,65.
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/nsmeta.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.
| Al-Haidari, 1/31/2021, Randomized Controlled Trial, Iraq, peer-reviewed, 3 authors, study period 5 September, 2020 - 15 November, 2020. | risk of death, 95.8% lower, RR 0.04, p = 0.001, treatment 0 of 160 (0.0%), control 14 of 259 (5.4%), NNT 18, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| risk of severe case, 92.6% lower, RR 0.07, p < 0.001, treatment 2 of 160 (1.2%), control 44 of 259 (17.0%), NNT 6.4. | |
| 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, 24.0% lower, RR 0.76, p = 0.09, treatment 85 of 345 (24.6%), control 152 of 393 (38.7%), NNT 7.1, adjusted per study, odds ratio converted to relative risk, multivariable. |
| Ashraf, 11/3/2020, Randomized Controlled Trial, placebo-controlled, Pakistan, peer-reviewed, 29 authors, study period 30 April, 2020 - 29 July, 2020, this trial uses multiple treatments in the treatment arm (combined with honey) - results of individual treatments may vary, trial NCT04347382 (history) (HNS-COVID-PK). | risk of death, 81.9% lower, RR 0.18, p = 0.01, treatment 2 of 157 (1.3%), control 11 of 156 (7.1%), NNT 17, all cases. |
| risk of death, 67.1% lower, RR 0.33, p = 0.49, treatment 0 of 107 (0.0%), control 1 of 103 (1.0%), NNT 103, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), moderate cases. | |
| risk of death, 78.8% lower, RR 0.21, p = 0.03, treatment 2 of 50 (4.0%), control 10 of 53 (18.9%), NNT 6.7, severe cases. | |
| risk of no recovery, 83.6% lower, HR 0.16, p < 0.001, treatment 107, control 103, inverted to make HR<1 favor treatment, moderate cases. | |
| risk of no recovery, 75.2% lower, HR 0.25, p < 0.001, treatment 50, control 53, inverted to make HR<1 favor treatment, severe cases. | |
| risk of no viral clearance, 81.9% lower, HR 0.18, p < 0.001, treatment 107, control 103, inverted to make HR<1 favor treatment, moderate cases. | |
| risk of no viral clearance, 76.9% lower, HR 0.23, p < 0.001, treatment 50, control 53, inverted to make HR<1 favor treatment, severe cases. | |
| Bencheqroun, 5/7/2022, Double Blind Randomized Controlled Trial, placebo-controlled, USA, peer-reviewed, mean age 45.0, 25 authors, study period 27 May, 2021 - 27 September, 2021, trial NCT04914377 (history) (BOSS-001). | risk of hospitalization, 69.3% lower, RR 0.31, p = 0.44, treatment 0 of 29 (0.0%), control 1 of 23 (4.3%), NNT 23, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm). |
| time to sustained clinical response, 9.1% lower, HR 0.91, p = 0.78, treatment 28, control 23, inverted to make HR<1 favor treatment, Kaplan–Meier. | |
| time to sustained clinical response, 35.5% lower, HR 0.65, p = 0.25, treatment 28, control 23, inverted to make HR<1 favor treatment, Kaplan–Meier, high-risk patients. | |
| risk of no viral clearance, 43.5% lower, RR 0.57, p = 0.31, treatment 5 of 21 (23.8%), control 8 of 19 (42.1%), NNT 5.5, day 14. | |
| Idris, 1/15/2024, prospective, Nigeria, peer-reviewed, mean age 30.8, 8 authors, study period 27 October, 2020 - 20 May, 2021. | recovery time, 39.0% lower, relative time 0.61, p = 0.003, treatment mean 4.5 (±1.51) n=26, control mean 7.38 (±2.2) n=25. |
| risk of no viral clearance, 15.4% lower, RR 0.85, p = 1.00, treatment 3 of 13 (23.1%), control 6 of 22 (27.3%), NNT 24, day 5. | |
| risk of no viral clearance, 40.5% lower, RR 0.60, p = 0.02, treatment 13 of 26 (50.0%), control 21 of 25 (84.0%), NNT 2.9, day 2. | |
| Koshak, 8/15/2021, Randomized Controlled Trial, Saudi Arabia, peer-reviewed, 10 authors, study period 1 May, 2020 - 30 September, 2020, trial NCT04401202 (history). | risk of hospitalization, 74.7% lower, RR 0.25, p = 0.37, treatment 1 of 91 (1.1%), control 4 of 92 (4.3%), NNT 31. |
| risk of no recovery, 42.7% lower, RR 0.57, p < 0.001, treatment 34 of 91 (37.4%), control 60 of 92 (65.2%), NNT 3.6. | |
| Said (B), 11/8/2022, Randomized Controlled Trial, Egypt, peer-reviewed, 5 authors, study period 21 July, 2021 - 30 December, 2021, trial NCT04981743 (history). | risk of no recovery, 77.0% lower, OR 0.23, p = 0.09, treatment 30, control 30, adjusted per study, multivariable, dyspnea, RR approximated with OR. |
| risk of no recovery, 89.0% lower, OR 0.11, p = 0.01, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, dyspnea, RR approximated with OR. | |
| risk of no recovery, 80.0% lower, OR 0.20, p = 0.003, treatment 30, control 30, adjusted per study, multivariable, cough, RR approximated with OR. | |
| risk of no recovery, 77.0% lower, OR 0.23, p = 0.01, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, cough, RR approximated with OR. | |
| risk of no recovery, 85.0% lower, OR 0.15, p = 0.003, treatment 30, control 30, adjusted per study, multivariable, fatigue, RR approximated with OR. | |
| risk of no recovery, 90.0% lower, OR 0.10, p < 0.001, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, fatigue, RR approximated with OR. | |
| risk of no recovery, 85.0% lower, OR 0.15, p = 0.04, treatment 30, control 30, adjusted per study, multivariable, smell, RR approximated with OR. | |
| risk of no recovery, 67.0% lower, OR 0.33, p = 0.23, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, smell, RR approximated with OR. | |
| risk of no recovery, 58.0% lower, OR 0.42, p = 0.28, treatment 30, control 30, adjusted per study, multivariable, taste, RR approximated with OR. | |
| risk of no recovery, 58.0% lower, OR 0.42, p = 0.28, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, taste, RR approximated with OR. | |
| risk of no recovery, 82.0% lower, OR 0.18, p = 0.05, treatment 30, control 30, sore throat, RR approximated with OR. | |
| risk of no recovery, 86.0% lower, OR 0.14, p = 0.03, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, sore throat, RR approximated with OR. | |
| risk of no recovery, 27.0% lower, OR 0.73, p = 0.62, treatment 30, control 30, headache, RR approximated with OR. | |
| risk of no recovery, 56.0% lower, OR 0.44, p = 0.21, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, headache, RR approximated with OR. | |
| risk of no recovery, 80.0% lower, OR 0.20, p = 0.05, treatment 30, control 30, diarrhea, RR approximated with OR. | |
| risk of no recovery, 90.0% lower, OR 0.10, p = 0.03, treatment 30, control 30, adjusted per study, vitamin D and nigella sativa, multivariable, diarrhea, RR approximated with OR. | |
| risk of no viral clearance, 61.0% lower, OR 0.39, p = 0.08, treatment 30, control 30, day 14, RR approximated with OR. | |
| risk of no viral clearance, 85.0% lower, OR 0.15, p = 0.004, treatment 30, control 30, day 7, RR approximated with OR. | |
| risk of no viral clearance, 91.0% lower, OR 0.09, p < 0.001, treatment 30, control 30, vitamin D and nigella sativa, day 14, RR approximated with OR. | |
| risk of no viral clearance, 87.0% lower, OR 0.13, p = 0.003, treatment 30, control 30, vitamin D and nigella sativa, day 7, RR approximated with OR. |
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.
| Faruq, 9/1/2023, Randomized Controlled Trial, Bangladesh, peer-reviewed, 4 authors, excluded in exclusion analyses: potential data issue. | risk of death, 6.5% lower, RR 0.94, p = 0.87, treatment 29 of 75 (38.7%), control 31 of 75 (41.3%), NNT 37. |
| risk of mechanical ventilation, 61.9% lower, RR 0.38, p = 0.01, treatment 8 of 75 (10.7%), control 21 of 75 (28.0%), NNT 5.8, day 14. | |
| risk of mechanical ventilation, 83.3% lower, RR 0.17, p < 0.001, treatment 3 of 75 (4.0%), control 18 of 75 (24.0%), NNT 5.0, day 7. | |
| ICU stay, 23.5% lower, RR 0.77, p = 0.74, treatment 4 of 46 (8.7%), control 5 of 44 (11.4%), NNT 37, >28 days. | |
| ICU stay, 28.3% lower, RR 0.72, p = 0.46, treatment 9 of 46 (19.6%), control 12 of 44 (27.3%), NNT 13, >21 days. | |
| ICU stay, 33.6% lower, RR 0.66, p = 0.007, treatment 25 of 46 (54.3%), control 36 of 44 (81.8%), NNT 3.6, >14 days. | |
| ICU stay, 6.6% lower, RR 0.93, p = 0.43, treatment 41 of 46 (89.1%), control 42 of 44 (95.5%), NNT 16, >7 days. | |
| Karimi, 10/4/2021, Randomized Controlled Trial, Iran, peer-reviewed, 37 authors, study period March 2020 - July 2020, this trial uses multiple treatments in the treatment arm (combined with several herbal medicines) - results of individual treatments may vary. | risk of death, 50.8% lower, RR 0.49, p = 0.45, treatment 2 of 192 (1.0%), control 4 of 189 (2.1%), NNT 93. |
| risk of ICU admission, 60.6% lower, RR 0.39, p = 0.28, treatment 2 of 192 (1.0%), control 5 of 189 (2.6%), NNT 62. | |
| hospitalization time, 70.0% lower, HR 0.30, p < 0.001, treatment 184, control 174, Cox proportional hazards, primary outcome. | |
| fever, 66.5% lower, OR 0.33, p = 0.001, treatment 184, control 174, inverted to make OR<1 favor treatment, RR approximated with OR. | |
| dyspnea, 13.7% lower, OR 0.86, p < 0.001, treatment 184, control 174, inverted to make OR<1 favor treatment, RR approximated with OR. | |
| Setayesh, 6/3/2022, Randomized Controlled Trial, Iran, peer-reviewed, mean age 59.1, 7 authors, study period June 2020 - September 2020, this trial uses multiple treatments in the treatment arm (combined with glycyrrhiza glabra, punica granatum, and rheum palmatum) - results of individual treatments may vary, trial IRCT20200330046899N1. | risk of death, 7.9% higher, RR 1.08, p = 1.00, treatment 1 of 38 (2.6%), control 1 of 41 (2.4%). |
| oxygen time, 26.8% lower, relative time 0.73, p = 0.007, treatment mean 3.0 (±1.6) n=38, control mean 4.1 (±1.9) n=41. | |
| hospitalization time, 28.7% lower, relative time 0.71, p < 0.001, treatment mean 5.7 (±1.9) n=38, control mean 8.0 (±1.8) n=41. |
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.
| Al-Haidari (B), 1/31/2021, prospective, Iraq, peer-reviewed, 3 authors. | risk of symptomatic case, 62.2% lower, RR 0.38, p < 0.001, treatment 68 of 188 (36.2%), control 180 of 188 (95.7%), NNT 1.7. |
| Chandra, 7/5/2022, Randomized Controlled Trial, India, peer-reviewed, 12 authors, study period 18 September, 2020 - 21 May, 2021, this trial uses multiple treatments in the treatment arm (combined with Infuza polyherbal formulation) - results of individual treatments may vary, trial CTRI/2020/08/027222. | risk of case, 49.0% lower, RR 0.51, p = 0.36, treatment 4 of 52 (7.7%), control 8 of 53 (15.1%), NNT 14, Infuza. |
| risk of case, 87.0% lower, RR 0.13, p = 0.03, treatment 1 of 51 (2.0%), control 8 of 53 (15.1%), NNT 7.6, Infuza and Kulzam. | |
| risk of case, 74.0% lower, RR 0.26, p = 0.09, treatment 2 of 51 (3.9%), control 8 of 53 (15.1%), NNT 9.0, Kulzam. | |
| Daneshfard, 7/16/2023, Randomized Controlled Trial, Iran, peer-reviewed, mean age 39.5 (treatment) 34.0 (control), 16 authors, study period 16 June, 2021 - 22 May, 2022, this trial uses multiple treatments in the treatment arm (combined with olea europaea oil) - results of individual treatments may vary, trial IRCT20210515051305N1. | risk of symptomatic case, 34.1% lower, RR 0.66, p = 0.006, treatment 37 of 89 (41.6%), control 53 of 84 (63.1%), NNT 4.6, any symptom. |
| risk of symptomatic case, 97.3% lower, RR 0.03, p < 0.001, treatment 1 of 89 (1.1%), control 35 of 84 (41.7%), NNT 2.5, fever. | |
| risk of symptomatic case, 65.7% lower, RR 0.34, p = 0.06, treatment 4 of 89 (4.5%), control 11 of 84 (13.1%), NNT 12, chest pain. | |
| risk of symptomatic case, 62.2% lower, RR 0.38, p = 0.10, treatment 4 of 89 (4.5%), control 10 of 84 (11.9%), NNT 13, loss of taste/smell. | |
| risk of symptomatic case, 26.0% lower, RR 0.74, p = 0.16, treatment 29 of 89 (32.6%), control 37 of 84 (44.0%), NNT 8.7, muscle ache. | |
| risk of symptomatic case, 6.2% higher, RR 1.06, p = 1.00, treatment 9 of 89 (10.1%), control 8 of 84 (9.5%), chills. | |
| risk of symptomatic case, 79.0% lower, RR 0.21, p = 0.001, treatment 4 of 89 (4.5%), control 18 of 84 (21.4%), NNT 5.9, cough. | |
| risk of symptomatic case, 76.4% lower, RR 0.24, p < 0.001, treatment 5 of 89 (5.6%), control 20 of 84 (23.8%), NNT 5.5, headache. | |
| risk of symptomatic case, 98.1% lower, RR 0.02, p < 0.001, treatment 0 of 89 (0.0%), control 25 of 84 (29.8%), NNT 3.4, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), vomiting. | |
| 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, 0.2% lower, RR 1.00, p = 1.00, treatment 4 of 39 (10.3%), control 22 of 214 (10.3%), NNT 4173, unadjusted, severe vs. mild cases. |
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