Vitamin B9 for COVID-19: real-time meta-analysis of 18 studies (12 treatment studies and 6 sufficiency studies)

@CovidAnalysis, October 2026, Version 9V9 (V1 2023)
Abstract
Meta-analysis using the most serious outcome reported shows 8% [-18‑41%] higher risk, without reaching statistical significance.
6 sufficiency studies analyze outcomes based on serum levels, showing 22% [7‑34%] lower risk for patients with higher vitamin B9 levels.
Results to date are contradictory. Several studies show higher mortality, however counfounding by indication may be significant — patients prescribed folic acid may have significantly higher risk on average. Studies independent of prescriptions based on patient condition show positive results1,2, as do sufficiency studies. Folic acid may not be the most effective or safest form for supplementation3. Studies show that a significant fraction of people have genetic variations limiting the ability to convert folic acid to the active form.
All data and sources to reproduce this analysis are in the appendix.
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Evolution of COVID-19 clinical evidence Meta-analysis results over time Vitamin B9 p=0.6 Vitamin D p<0.0000000001 2020 2021 2022 2023 2024 2025 2026 Lowerrisk Higherrisk c19early.org October 2026 50% 0% -50%
Vitamin B9 for COVID-19 — Highlights
Meta-analysis of studies to date shows no significant improvements with vitamin B9.
Results are contradictory. Several studies show higher mortality, however counfounding by indication may be significant — patients prescribed folic acid may have higher risk on average. Folic acid may not be the best form for treatment.
Real-time updates and corrections with a consistent protocol for 226 treatments. Outcome specific analysis and combined evidence from all studies including treatment delay, a primary confounding factor.
c19early.org
October 2026

Vitamin B9 COVID-19 studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bejan9%0.91 · 0.33–2.53death353 (n)8,853 (n) Meisel27%0.73 · 0.26–2.04death23 (n)310 (n) Bliek-Bueno−87%1.87 · 1.51–2.33death8,570 (all patients)CT1 Deschasaux-Tanguy16%0.84 · 0.72–0.98cases7,766 (all patients)per SD change Monserrat .. (PSM)−132%2.32 · 1.36–4.08deathn/an/a Nimer28%0.72 · 0.42–1.23hosp.16/213203/1,935 MacFadden0%1.00 · 0.93–1.07casesn/an/a Loucera1%0.99 · 0.81–1.20death624 (n)15,344 (n) Topless−164%2.64 · 2.15–3.24deathpopulation-based cohort Farag (CLUS. RCT)88%0.12 · 0.04–0.36cases4/22420/139 Akbar−18%1.18 · 0.83–1.66cases316 (n)9,684 (n) Zhang40%0.60 · 0.26–1.38cases566 (n)34 (n)
Prophylaxis−8%1.08 · 0.82–1.4120/2,319223/36,2998% higher risk
Tau² = 0.16, I² = 92.4%, p = 0.6
All studies−8%1.08 · 0.82–1.4120/2,319223/36,2998% higher risk
Tau² = 0.16, I² = 92.4%, p = 0.600.511.52+
1 CT: study uses combined treatment
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← Vitamin B9
reduces riskVitamin B9
increases risk →
B
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Fig. 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 vitamin B9 studies.
Introduction
Fig. 2. SARS-CoV-2 spike protein fibrin binding leads to thromboinflammation and neuropathology, from4.
Immediate treatment recommended
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 injury5-21 and cognitive deficits8,13, cardiovascular complications22-28, DNA damage29-32, organ failure, and death. Even mild untreated infections may result in persistent cognitive deficits33—the spike protein binds to fibrin leading to fibrinolysis-resistant blood clots, thromboinflammation, and neuropathology. Minimizing replication as early as possible is recommended.
Many treatments are expected to modulate infection
SARS-CoV-2 infection and replication involves the complex interplay of 500+ host and viral proteins and other factorsA,34-41, providing many therapeutic targets for which many existing compounds have known activity. Scientists have predicted that over 12,000 compounds may reduce COVID-19 risk42, either by directly minimizing infection or replication, by supporting immune system function, or by minimizing secondary complications.
Extensive supporting research
Vitamin B9 has been identified by the European Food Safety Authority (EFSA) as having sufficient evidence for a causal relationship between intake and optimal immune system function43-45. Vitamin B9 inhibits SARS-CoV-2 in silico46-54, reduces spike protein binding ability46, binds with the spike protein receptor binding domain for alpha and omicron variants55, inhibits the SARS-CoV-2 nucleocapsid protein53, inhibits 3CLpro and PLpro in enzymatic assays55, significantly reduces infection for alpha and omicron SARS-CoV-2 pseudoviruses55, and inhibits ACE2 expression and SARS-CoV-2 infection in a mouse model46.
Analysis
We analyze all significant controlled studies of vitamin B9 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, individual outcomes, and Randomized Controlled Trials (RCTs).
Treatment timing
Fig. 3 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.
regular treatment to prevent or minimize infectionstreat immediately on symptoms or shortly thereafterlate stage after disease progressionexposed to virusEarly TreatmentProphylaxisTreatment delayLate Treatment
Fig. 3. Treatment stages.
Preclinical Research
Vitamin B9 inhibits SARS-CoV-2 in silico46-54, reduces spike protein binding ability46, binds with the spike protein receptor binding domain for alpha and omicron variants55, inhibits the SARS-CoV-2 nucleocapsid protein53, inhibits 3CLpro and PLpro in enzymatic assays55, significantly reduces infection for alpha and omicron SARS-CoV-2 pseudoviruses55, and inhibits ACE2 expression and SARS-CoV-2 infection in a mouse model46.
9 in silico studies support the efficacy of vitamin B947-53,55,56.
4 in vitro studies support the efficacy of vitamin B946,53-55.
An in vivo animal study supports the efficacy of vitamin B946.
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.
Results
Table 1 summarizes the results for all studies, for Randomized Controlled Trials, and for specific outcomes. Fig. 4, 5, 6, 7, 8, 9, and 10 show forest plots for random-effects meta-analysis of all studies with pooled effects, mortality results, ventilation, ICU admission, hospitalization, cases, and sufficiency studies.
Table 1. Random-effects meta-analysis for all studies, for Randomized Controlled Trials, and for specific outcomes. Results show the relative risk with treatment and the 95% confidence interval. *** p<0.001.
Relative Risk Studies Patients
All studies1.08 [0.82‑1.41]1250K
RCTsRCTs0.12 [0.04‑0.36]***1363
Mortality1.53 [0.98‑2.40]630K
Cases0.93 [0.69‑1.24]610K
c19early.org
October 2026

Vitamin B9 COVID-19 studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bejan9%0.91 · 0.33–2.53death353 (n)8,853 (n) Meisel27%0.73 · 0.26–2.04death23 (n)310 (n) Bliek-Bueno−87%1.87 · 1.51–2.33death8,570 (all patients)CT1 Deschasaux-Tanguy16%0.84 · 0.72–0.98cases7,766 (all patients)per SD change Monserrat .. (PSM)−132%2.32 · 1.36–4.08deathn/an/a Nimer28%0.72 · 0.42–1.23hosp.16/213203/1,935 MacFadden0%1.00 · 0.93–1.07casesn/an/a Loucera1%0.99 · 0.81–1.20death624 (n)15,344 (n) Topless−164%2.64 · 2.15–3.24deathpopulation-based cohort Farag (CLUS. RCT)88%0.12 · 0.04–0.36cases4/22420/139 Akbar−18%1.18 · 0.83–1.66cases316 (n)9,684 (n) Zhang40%0.60 · 0.26–1.38cases566 (n)34 (n)
Prophylaxis−8%1.08 · 0.82–1.4120/2,319223/36,2998% higher risk
Tau² = 0.16, I² = 92.4%, p = 0.6
All studies−8%1.08 · 0.82–1.4120/2,319223/36,2998% higher risk
Tau² = 0.16, I² = 92.4%, p = 0.600.511.52+
1 CT: study uses combined treatment
Rotate screen for more detailsIncrease width for more details
← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 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.
c19early.org
October 2026

Vitamin B9 COVID-19 mortality results

StudyImprovementRR · 95% CITreatmentControlRelative Risk
Bejan9%0.91 · 0.33–2.53353 (n)8,853 (n) Meisel27%0.73 · 0.26–2.0423 (n)310 (n) Bliek-Bueno−87%1.87 · 1.51–2.338,570 (all patients)CT1 Monserrat .. (PSM)−132%2.32 · 1.36–4.08n/an/a Loucera1%0.99 · 0.81–1.20624 (n)15,344 (n) Topless−164%2.64 · 2.15–3.24population-based cohort
Prophylaxis−53%1.53 · 0.98–2.401,000 (n)24,507 (n)53% higher risk
Tau² = 0.24, I² = 91.1%, p = 0.063
All studies−53%1.53 · 0.98–2.401,000 (n)24,507 (n)53% higher risk
Tau² = 0.24, I² = 91.1%, p = 0.06300.511.52+
1 CT: study uses combined treatment
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 5. Random-effects meta-analysis for mortality results.
c19early.org
October 2026

Vitamin B9 COVID-19 mechanical ventilation results

StudyImprovementRR · 95% CITreatmentControlRelative Risk
Bejan1%0.99 · 0.38–2.53355 (n)8,874 (n)
Prophylaxis1%0.99 · 0.38–2.56355 (n)8,874 (n)1% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.99
All studies1%0.99 · 0.38–2.56355 (n)8,874 (n)1% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.9900.511.52+
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 6. Random-effects meta-analysis for ventilation.
c19early.org
October 2026

Vitamin B9 COVID-19 ICU results

StudyImprovementRR · 95% CITreatmentControlRelative Risk
Bejan17%0.83 · 0.34–2.02356 (n)8,911 (n)
Prophylaxis17%0.83 · 0.34–2.02356 (n)8,911 (n)17% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.7
All studies17%0.83 · 0.34–2.02356 (n)8,911 (n)17% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.700.511.52+
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 7. Random-effects meta-analysis for ICU admission.
c19early.org
October 2026

Vitamin B9 COVID-19 hospitalization results

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Nimer28%0.72 · 0.42–1.23hosp.16/213203/1,935
Prophylaxis28%0.72 · 0.44–1.1816/213203/1,93528% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.19
All studies28%0.72 · 0.44–1.1816/213203/1,93528% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.1900.511.52+
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 8. Random-effects meta-analysis for hospitalization.
c19early.org
October 2026

Vitamin B9 COVID-19 case results

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Deschasaux-Tanguy16%0.84 · 0.72–0.98cases7,766 (all patients)per SD change MacFadden0%1.00 · 0.93–1.07casesn/an/a Topless−51%1.51 · 1.42–1.61casespopulation-based cohort Farag (CLUS. RCT)88%0.12 · 0.04–0.36cases4/22420/139 Akbar−18%1.18 · 0.83–1.66cases316 (n)9,684 (n) Zhang40%0.60 · 0.26–1.38cases566 (n)34 (n)
Prophylaxis7%0.93 · 0.69–1.244/1,10620/9,8577% lower risk
Tau² = 0.10, I² = 95.9%, p = 0.62
All studies7%0.93 · 0.69–1.244/1,10620/9,8577% lower risk
Tau² = 0.10, I² = 95.9%, p = 0.6200.511.52+
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 9. Random-effects meta-analysis for cases.
c19early.org
October 2026

Vitamin B9 COVID-19 sufficiency studies

StudyImprovementRR · 95% CIOutcomeHigh LevelsLow LevelsRelative Risk
Meisel15%0.85 · 0.41–1.75death296 (n)38 (n) Doğan56%0.44 · 0.04–4.51death2/541/12 Voelkle12%0.88 · 0.78–0.98death/ICUn/an/aper SD change Keskin32%0.68 · 0.56–0.82hosp. time132 (n)132 (n) Abdulrahman−75%1.75 · 0.19–16.67death72 (n)9 (n) Mohamed43%0.57 · 0.29–1.12death10/3711/23
All studies22%0.78 · 0.66–0.9312/59112/21422% lower risk
Tau² = 0.01, I² = 30.4%, p = 0.004500.511.52+
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← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 10. Random-effects meta-analysis for sufficiency 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.
Randomized Controlled Trials (RCTs)
Fig. 11 shows a forest plot for random-effects meta-analysis of all Randomized Controlled Trials. RCT results are included in Table 1. Currently there is only one RCT.
RCTs have many potential biases
RCTs help to make study groups more similar and can provide a higher level of evidence, however they are subject to many biases57, and analysis of double-blind RCTs has identified extreme levels of bias58. 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.
Conflicts of interest for COVID-19 RCTs
RCTs are expensive and many RCTs are funded by pharmaceutical companies or other organizations with conflicts of interest, for example governments that previously denied treatment with the study drug. 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. Bekelman et al. and Lundh et al. show that industry-sponsored studies are more likely to be favorable. For COVID-19, some major philanthropic organizations are largely funded by investments with extreme conflicts of interest for and against specific COVID-19 interventions.
RCTs for novel acute diseases requiring rapid treatment
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 226 treatments we have analyzed, 67% 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.
RCTs may be less reliable
Concato et al. report a paradoxical finding—RCT results had higher variability, and only RCTs were found to sometimes report significant results the opposite of the overall result. The same trend is seen for the most popular (most politicized) COVID-19 treatments—considering all statistically significant results reported in studies, RCTs are slightly more likely to report a result in the opposite direction. In other words, for these COVID-19 treatments and for the topics covered by Concato et al., assuming causality from a single study is more likely to result in an incorrect conclusion for RCTs.
Increased risk of inconsistent results for RCTs suggests higher prevalence of bias, which may arise due to many issues including design bias, conflicts of interest, treatment differences by physicians aware of allocation, attrition bias, ascertainment bias, randomization failures, errors, or fraud.
Using all studies identifies efficacy 8+ months faster (9+ months for low-cost treatments)
Currently, 59 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, 54% have been confirmed in RCTs, with a mean delay of 7.8 months (62% with 8.7 months delay for low-cost treatments). The remaining treatments either have no RCTs, or the point estimate is consistent.
All studies must be carefully analyzed
Neither observational studies nor RCTs prove causation—any study can be flawed or fraudulent. We need much more, for example a combination of results from many independent teams, detailed understanding of each study, knowledge of conflicts/team reliability, dose-response relationships, delay-response relationships, logical results across outcomes, or details consistent with preclinical expectations.
All studies must be evaluated individually. 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.
c19early.org
October 2026

Vitamin B9 COVID-19 Randomized Controlled Trials

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Farag (CLUS. RCT)88%0.12 · 0.04–0.36cases4/22420/139
Prophylaxis88%0.12 · 0.04–0.364/22420/13988% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.00012
All studies88%0.12 · 0.04–0.364/22420/13988% lower risk
Tau² = 0.00, I² = 0.0%, p = 0.0001200.511.52+
Rotate screen for more detailsIncrease width for more details
← Vitamin B9
reduces riskVitamin B9
increases risk →
Fig. 11. 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.
Media Censorship
Low-cost treatments were subject to bias and censorship during the pandemic. Scientific bias is seen in the design, analysis, presentation, and selective reporting of studies, which often favored negative results. A similar bias is seen in the media coverage for low-cost treatments. While broadly seen, bias was particularly notable for ivermectin and hydroxychloroquine, e.g., Scott Alexander noted that "if you say anything in favor of ivermectin you will be cast out of civilization and thrown into the circle of social hell reserved for Klan members and 1/6 insurrectionists. All the health officials in the world will shout 'horse dewormer!' at you and compare you to Josef Mengele."63.
We analyze media coverage for the 226 treatments we cover using Altmetric64, which reports the number of ~12,000 tracked news outlets that covered each study65. Studies are considered to have received significant media coverage if they were covered by at least 0.5% of the tracked news outlets. Fig. 12, 13, and 14 show the bias toward negative results for low-cost treatments, in contrast to the opposite bias for high-profit treatments. This may result in widespread incorrect perceptions on the relative efficacy of high-profit and low-cost treatments. The impact is significant—increased cost limits the use of high-profit treatments and treatment equity, and high-profit treatments were also more difficult to access, especially for earlier treatment which improves efficacy and minimizes community transmission.
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Fig. 12. Media was more likely to cover negative or inconclusive results for low-cost treatments, and positive results for high-profit treatments.
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Fig. 13. Mainstream media was biased against positive results for low-cost treatments.
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Fig. 14. In contrast to the results for low-cost treatments, mainstream media was biased towards positive results for high-cost treatments.
A combination of factors may have led to the media's suppression of low-cost treatments:
•
Politicization
led to a media environment where coverage was often framed to support a political narrative rather than to provide objective scientific information. As Scott Alexander said:
"if you say anything in favor of ivermectin you will be cast out of civilization and thrown into the circle of social hell reserved for Klan members and 1/6 insurrectionists. All the health officials in the world will shout 'horse dewormer!' at you and compare you to Josef Mengele."
There was strong social pressure to discredit low-cost treatments.
•
Censorship
of information conflicting with selected authorities. For example, individuals and organizations presenting conflicting science were often banned on Twitter and YouTube.
•
FDA requires "no adequate, approved, and available alternatives"
in order to grant an EUA for novel high-profit interventions, creating a strong incentive for authorities to ignore or downplay existing low-cost treatments.
•
Regulatory capture
biases authorities towards high-profit interventions.
•
Authorities ignored most evidence for low-cost treatments
, for example the NIH references only 2% of studies in delayed, rarely-updated, biased commentaries with no quantitive analysis.
•
Media coverage of science is often not very accurate
, e.g., misunderstanding confounding issues. For example the media widely considered the RECOVERY HCQ RCT to be conclusive on efficacy, but very late treatment of late stage patients (mostly on oxygen already) with an excessive toxic dose (shown dangerous in a dose comparison RCT) provides no information on the recommended early/prophylactic treatment. With difficulting in understanding basic confounders like treatment delay and dose, the media may favor deferring to authorities. Many studies for low-cost treatments require greater expertise to analyze. Relatively few journalists have a strong ability to analyze clinical trials and are outnumbered by the rest.
•
Substantial funding from pharmaceutical advertising
biases editorial decisions towards high-profit interventions.
•
PR power
- companies/teams with strong PR presence are favored in the media, which correlates with high-profit and high conflict of interest studies.
•
The media was very negative in general
, inflating risk, fear, and anxieties. A negative bias may improve ratings and revenue, increasing motivation to continue watching coverage. A combination of low-cost treatments greatly reducing risk conflicts with the negative narrative.
Heterogeneity
Heterogeneity in COVID-19 studies arises from many factors including:
Treatment delay
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 hours66,67. 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 (B) et al. report only 2.5 hours improvement for inpatient treatment.
Table 2. Studies of baloxavir marboxil for influenza show that early treatment is more effective.
Treatment delayResult
Post-exposure prophylaxis86% fewer cases68
<24 hours-33 hours symptoms69
24-48 hours-13 hours symptoms69
Inpatients-2.5 hours to improvement70
Fig. 15 shows a mixed-effects meta-regression for efficacy as a function of treatment delay in COVID-19 studies from 226 treatments, showing that efficacy declines rapidly with treatment delay. Early treatment is critical for COVID-19.
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Fig. 15. Early treatment is more effective. Meta-regression showing efficacy as a function of treatment delay in COVID-19 studies from 226 treatments.
Patient demographics
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.
SARS-CoV-2 variants
Efficacy may depend critically on the distribution of SARS-CoV-2 variants encountered by patients. Risk varies significantly across variants72, for example the Gamma variant shows significantly different characteristics73-76. 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 variants77,78.
Treatment regimen
Effectiveness may depend strongly on the dosage and treatment regimen.
Medication quality
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.
Other treatments
The use of other treatments may significantly affect outcomes, including supplements, other medications, or other interventions such as prone positioning. Treatments may be synergistic81-105, therefore efficacy may depend strongly on combined treatments.
Effect measured
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.
Meta-analysis
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.
Pooled Effects
Combining studies is required
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.
Specific outcome and pooled analyses
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.
Ethical and practical issues limit high-risk trials
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.
Validating pooled outcome analysis for COVID-19
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 226 treatments we cover confirms the validity of pooled outcome analysis for COVID-19. Fig. 16 shows that lower hospitalization is very strongly associated with lower mortality (p < 0.0000000001). Similarly, Fig. 17 shows that improved recovery is very strongly associated with lower mortality (p < 0.0000000001). 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. Fig. 18 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 = 0.0000000074 to p = 0.00000000015.
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Fig. 16. Lower hospitalization is associated with lower mortality, supporting pooled outcome analysis.
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Fig. 17. Improved recovery is associated with lower mortality, supporting pooled outcome analysis.
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Fig. 16. Improved viral clearance is associated with fewer serious outcomes, supporting pooled outcome analysis.
Pooled outcomes identify efficacy 5 months faster (7 months for RCTs)
Currently, 59 of the treatments we analyze show statistically significant efficacy or harm, defined as ≥10% decreased risk or >0% increased risk from ≥3 studies. 85% of these have been confirmed with one or more specific outcomes, with a mean delay of 4.6 months. When restricting to RCTs only, 53% of treatments showing statistically significant efficacy/harm with pooled effects have been confirmed with one or more specific outcomes, with a mean delay of 7.5 months. Fig. 19 shows when treatments were found effective during the pandemic. Pooled outcomes often resulted in earlier detection of efficacy.
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Fig. 19. 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.
Limitations
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 differences in treatment delay are more likely to hide efficacy.
Summary
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.
Discussion
Publication bias
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 results107-110. For vitamin B9, there is currently not enough data to evaluate publication bias with high confidence.
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. Fig. 20 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 < 0.05111-118. 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.
Log Risk Ratio Standard Error 1.406 1.055 0.703 0.352 0 -3 -2 -1 0 1 2 A: Simulated perfect trials p > 0.05 Log Risk Ratio Standard Error 1.433 1.074 0.716 0.358 0 -4 -3 -2 -1 0 1 2 B: Simulated perfect trials with varying treatment delay p < 0.0001
Fig. 20. Example funnel plot analysis for simulated perfect trials.
Conflicts of interest
Pharmaceutical drug trials often have conflicts of interest whereby sponsors or trial staff have a financial interest in the outcome being positive. Vitamin B9 for COVID-19 lacks this because it is off-patent, has multiple manufacturers, and is very low cost. In contrast, most COVID-19 vitamin B9 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 vitamin B9 trials represent the optimal conditions for efficacy.
Limitations
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 alone81-105. 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.
Notes
1 of 12 studies combine treatments. The results of vitamin B9 alone may differ. None of the RCTs use combined treatment. Currently all studies are peer-reviewed.
Reviews
Multiple reviews cover vitamin B9 for COVID-19, presenting additional background on mechanisms and related results, including3,119,120.
Other studies
Srivastava et al. also suggests potential benefits of vitamin B9 for COVID-19. We have not reviewed this paper in detail.
Perspective
Results compared with other treatments
SARS-CoV-2 infection and replication involves a complex interplay of 500+ host and viral proteins and other factors34-41, providing many therapeutic targets. Over 12,000 compounds have been predicted to reduce COVID-19 risk42, either by directly minimizing infection or replication, by supporting immune system function, or by minimizing secondary complications. Fig. 21 shows an overview of the results for vitamin B9 in the context of multiple COVID-19 treatments, and Fig. 22 shows a plot of efficacy vs. cost for COVID-19 treatments.
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Fig. 21. Scatter plot showing results within the context of multiple COVID-19 treatments. Diamonds shows the results of random-effects meta-analysis. 0.5% of 12,000+ proposed treatments show efficacy132.
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Fig. 22. Efficacy vs. cost for COVID-19 treatments.
Conclusion
Meta-analysis using the most serious outcome reported shows 8% [-18‑41%] higher risk, without reaching statistical significance. 6 sufficiency studies analyze outcomes based on serum levels, showing 22% [7‑34%] lower risk for patients with higher vitamin B9 levels.
Results to date are contradictory. Several studies show higher mortality, however counfounding by indication may be significant — patients prescribed folic acid may have significantly higher risk on average. Studies independent of prescriptions based on patient condition show positive results1,2, as do sufficiency studies. Folic acid may not be the most effective or safest form for supplementation3. Studies show that a significant fraction of people have genetic variations limiting the ability to convert folic acid to the active form.
 
Contact.
Contact us on X at @CovidAnalysis.
Funding.
We have received no funding or compensation in any form, and do not accept donations. This is entirely volunteer work.
Conflicts of interest.
We have no conflicts of interest. We have no affiliation with any pharmaceutical companies, supplement companies, governments, political parties, or advocacy organizations.
AI.
We use AI models (Gemini, Grok, Claude, and ChatGPT) tasked with functioning as additional peer-reviewers to check for errors, suggest improvements, and review spelling and grammar. Any corrections are manually verified. Our preference for em dashes is independent of AI.
Updates.
Our COVID-19 meta-analyses involve the extraction of over 228,000 datapoints from thousands of papers for 226 treatments. We thank the thousands of scientists, physicians, and other contributors that have provided updates, suggestions, feedback, and corrections. These are all welcome and can be submitted at https://c19early.org/b9meta.html.
Dedication.
This work is dedicated to top evidence-based physicians that worked tirelessly to analyze evidence and greatly reduce mortality and morbidity during the pandemic. In alphabetical order: Dr. Thomas J. Borody, Dr. Mary Talley Bowden, Dr. Flavio Cadegiani, Dr. Shankara Chetty, Dr. Ryan Cole, Dr. George Fareed, Dr. Sabine Hazan, Dr. Pierre Kory, Dr. Tess Lawrie, Dr. Robert Malone, Dr. Paul Marik, Dr. Peter McCullough, Dr. Didier Raoult, Dr. Harvey Risch, Dr. Jackie Stone, Dr. Brian Tyson, Dr. Joseph Varon, and Dr. Vladimir Zelenko.
Public domain.
This is a public domain work distributed in accordance with the Creative Commons CC0 1.0 Universal license, which dedicates the work to the public domain by waiving all rights worldwide under copyright law. You can distribute, remix, adapt, and build upon this work in any medium or format, including for commercial purposes, without asking permission. Referenced material and third-party images retain any original copyrights or restrictions. See: https://creativecommons.org/publicdomain/zero/1.0/.
Study Notes
SufficiencyRetrospective · 81 patients · UK · Apr 2020 – May 2021
Vitamin B9 for COVID-19
Abdulrahman et al. Int. J. Psychiatry in Medicine · April 2023
Outcome
Improvement
Relative Risk · 95% CI
Mortality
-75%1.75 · 0.19 to >9
Progression, hosp./ICU/death
45%0.55 · 0.13–2.27
00.511.52+
← Vitamin B9
reduces riskVitamin B9
increases risk →
Lower progression with higher vitamin B9 levels
Not statistically significant · p = 0.42
Retrospective 81 pyschiatric inpatients in the UK, mean age 76, showing no significant difference in COVID-19 mortality with folate deficiency. Submit Corrections or Updates.
Retrospective 10,000 adults in Qatar, showing higher risk of COVID-19 cases with vitamin B9 supplementation, without statistical significance. Authors do not analyze COVID-19 severity. Submit Corrections or Updates.
Retrospective 9,748 COVID-19 patients in the USA showing no significant differences with vitamin B9 use, without statistical significance. Submit Corrections or Updates.
ProphylaxisRetrospective · 8,570 patients · multinational · Mar – Apr 2020
Vitamin B9 for COVID-19
Bliek-Bueno et al. Int. J. Environmental Research and Public Health · Nov 2021
Outcome
Improvement
Relative Risk · 95% CI
Mortality, combined
-87%1.87 · 1.51–2.33
Mortality, Campania
-170%2.70 · 1.83–3.99
Mortality, Aragon
-59%1.59 · 1.21–2.04
00.511.52+
← Vitamin B9
reduces riskVitamin B9
increases risk →
Higher mortality with vitamin B9 + Vitamin B12
p < 0.000001
Retrospective 8,570 individuals in Spain and Italy, showing higher mortality with combined vitamin B9 and B12 supplementation. Adjustments only considered age. Submit Corrections or Updates.
Analysis of 7,766 adults in France, showing higher intakes of vitamin C, folate, vitamin K, dietary fibre, and fruit and vegetables associated with lower seropositivity. Submit Corrections or Updates.
SufficiencyRetrospective · 66 patients · Turkey · Jan – Mar 2022
Vitamin B9 for COVID-19
Doğan et al. Sağlık Akademisi Kastamonu · April 2022
Outcome
Improvement
Relative Risk · 95% CI
Mortality
56%0.44 · 0.04–4.51
ICU admission
-11%1.11 · 0.14–8.67
00.511.52+
← Vitamin B9
reduces riskVitamin B9
increases risk →
Lower mortality with higher vitamin B9 levels
Not statistically significant · p = 0.46
Retrospective 70 COVID-19 cases and 70 non-COVID-19 controls in Turkey, showing no significant differences based on folic acid levels. Submit Corrections or Updates.
Cluster RCT 526 healthcare workers in Egypt, showing lower COVID-19 cases with folic acid supplementation, and a dose-response relationship. Each wave of health care workers was randomized within 14 day isolation periods, introducing potential confounding by time. Submit Corrections or Updates.
Retrospective 529 hospitalized COVID-19 patients in Turkey showing lower serum folic acid levels associated with longer hospitalization and higher mortality. Folic acid deficiency and insufficiency were common. There was no significant association for vitamin B12 levels and outcomes. Authors hypothesize that folic acid may support the immune response against SARS-CoV-2 and reduce inflammation. Submit Corrections or Updates.
Retrospective 15,968 COVID-19 hospitalized patients in Spain, showing no significant difference in mortality with existing use of folic acid. Since only hospitalized patients are included, results do not reflect different probabilities of hospitalization across treatments. Submit Corrections or Updates.
Retrospective 26,121 cases and 2,369,020 controls ≥65yo in Canada, showing no significant difference in cases with chronic use of vitamin B9. Submit Corrections or Updates.
Retrospective 333 hospitalized patients in Israel, showing no significant difference in outcomes with low folate levels or with folic acid supplementation. Submit Corrections or Updates.
Retrospective 60 hospitalized pediatric COVID-19 patients showing deficiencies in vitamin D, folic acid (B9), zinc, and selenium associated with higher mortality. Submit Corrections or Updates.
PSM retrospective 3,712 hospitalized patients in Spain, showing lower mortality with existing use of azithromycin, bemiparine, budesonide-formoterol fumarate, cefuroxime, colchicine, enoxaparin, ipratropium bromide, loratadine, mepyramine theophylline acetate, oral rehydration salts, and salbutamol sulphate, and higher mortality with acetylsalicylic acid, digoxin, folic acid, mirtazapine, linagliptin, enalapril, atorvastatin, and allopurinol. Submit Corrections or Updates.
ProphylaxisRetrospective · 2,148 patients · Jordan · Mar – Jul 2021
Vitamin B9 for COVID-19
Nimer et al. Bosnian J. Basic Medical Sciences · Feb 2022
Outcome
Improvement
Relative Risk · 95% CI
Hospitalization
28%0.72 · 0.42–1.23
Severe case
28%0.72 · 0.43–1.15
00.511.52+
← Vitamin B9
reduces riskVitamin B9
increases risk →
Lower hospitalization and severe cases
Not statistically significant · p = 0.23 (hospitalization) and p = 0.16 (severe cases)
Retrospective 2,148 COVID-19 recovered patients in Jordan, showing lower risk of severity and hospitalization with vitamin B9 prophylaxis, without statistical significance. Submit Corrections or Updates.
UK Biobank retrospective showing higher cases and mortality with folic acid supplementation. Submit Corrections or Updates.
Prospective study of 57 consecutive hospitalized COVID-19 patients in Switzerland, showing lower risk of mortality/ICU admission with vitamin B9. Adjustments only considered age. Submit Corrections or Updates.
Retrospective 600 pregnant women in an urban area of China showing a significantly lower risk of SARS-CoV-2 infection in late pregnancy with higher gestational ozone exposure levels. Ozone exposure, driven by photochemical reactions, is strongly correlated with sunlight in this urban population. There was a non-significant trend towards lower risk of COVID-19 with folic acid supplementation. Submit Corrections or Updates.
Appendix 1. Methods and Data
Search methods
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, which regularly receives notification of studies upon publication. Search terms are vitamin B9 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 vitamin B9 for COVID-19 that report a comparison with a control group are included in the main analysis. Studies with major unexplained data issues, for example major outcome data that is impossible to be correct with no response from the authors, are excluded.
Fig. 23. Mid-recovery results can more accurately reflect efficacy when almost all patients recover. Mateja et al. confirm that intermediate viral load results more accurately reflect hospitalization/death.
Effect extraction
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 reported then they are both used in specific outcome analyses, while mortality is used for pooled analysis. If symptomatic results are reported at multiple times, we use 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 outcomes. 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. An IPD meta-analysis confirms that intermediate viral load reduction is more closely associated with hospitalization/death than later viral load reduction133. 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.
Statistical methods
Forest plots are computed using PythonMeta134 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. When results provide an odds ratio, we compute the relative risk when possible, or convert to a relative risk according to Zhang (C) et al. Reported confidence intervals and p-values are used when available, and adjusted values are used 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 1138. 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 (3.14.7) with scipy (1.18.1), pythonmeta (1.26), numpy (2.5.3), statsmodels (0.15.0), and plotly (6.9.0). 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.
When evaluating potential effect modification across groups, we use an interaction test as described by Altman (C) et al. We compared the log-transformed relative risks using a z-test, deriving the standard error of the difference from the 95% confidence intervals. A two-sided interaction p-value of < 0.05 was considered a statistically significant difference in treatment effect between the groups.
Quality evaluation
Cochrane RoB 2/ROBINS-I are often used to evaluate studies, and have the advantage of providing standardized rules that can be applied with minimal understanding of the domain and study. However, the rules do not account for many real-world issues, often overemphasize or underemphasize others, and studies show low inter-rater reliability146. Certain domains are more applicable for these tools, however the time-sensitive nature of a pandemic, with significant mortality for every day of delay in evidence assessment, and the characteristics of COVID-19 make them inappropriate for this domain. This can be demonstrated with examples where expert RoB 2/ROBINS-I ratings do not match reality for COVID-19. Popp et al. use RoB 2 to classify Reis et al. as low risk of bias, however this is the opposite of reality—the trial not only has very high risk of bias, but has very high actual known bias, refusing to release data despite pledging to, reporting multiple impossible numbers, having blinding and randomization failure, and many other issues148. Axfors et al. use RoB 2 to classify Horby et al. as low risk of bias, however this is the opposite of reality—the very late treatment and excessive dosage used produces results with no relevance to recommended usage. HCQ shows poor results with late treatment and excessive dosage, and the combination shows harmB. Hempenius et al. use ROBINS-I to classify 33 studies for HCQ. The two rated as having the lowest risk of bias144,145 are far from the most informative. Both involve very late treatment, providing no information on recommended usage, and ROBINS-I does a very poor job of accounting for the impact of confounding factorsC.
Our quality evaluation focuses on known issues and bias, and the potential impact on outcomes, rather than just the risk of bias. The estimated potential impact of each confounding factor, and the direction of the impact is considered. For example, consider a study that shows significantly lower risk, the value of the study varies significantly if confounding points to an underestimate or an overestimate of efficacy. In one case, the real effect may be null, while the other case provides stronger evidence of efficacy (which may be greater than the study shows). Analysis focusing on the risk of bias, while simpler, may penalize studies for theoretical or technical issues that have no or minimal impact on outcomes. Analysis also depends on the outcome, for example certain issues are less relevant for objective outcomes such as mortality. Inaccurate penalization, and inaccurate high-quality evaluation in the face of known major issues affecting outcomes, increases in significance during a pandemic when immediate recognition of new evidence is critical, and when considering all global studies, as required during a pandemic. Investigators in other countries may have different customs for design, analysis, and reporting, and different English language skills, however they may not be less diligent or have greater bias. Investigators in lower-pharmaceutical-profit countries may have lower bias towards profitable interventions.
Treatment time
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 effective66,67.
Living analysis
This is a living analysis and is updated regularly. Submit updates or corrections with the form below. We received no funding, this research is done in our spare time. We have no affiliation with any pharmaceutical companies, supplement companies, governments, political parties, or advocacy organizations.
A summary of study results is below. Please submit updates and corrections at the bottom of this page.
A summary of study results is below. Please submit updates and corrections at https://c19early.org/b9meta.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.
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.
Akbar, 11/7/2023, retrospective, Qatar, peer-reviewed, mean age 40.3, 9 authors, study period March 2020 - September 2020.
Submit Corrections or Updates.
 risk of case, 18.0% higher, OR 1.18, p = 0.29, treatment 316, control 9,684, adjusted per study, multivariable, model 2, RR approximated with OR.
Bejan, 2/28/2021, retrospective, USA, peer-reviewed, mean age 42.0, 6 authors.
Submit Corrections or Updates.
 risk of death, 9.0% lower, OR 0.91, p = 0.87, treatment 353, control 8,853, adjusted per study, RR approximated with OR.
risk of mechanical ventilation, 1.0% lower, OR 0.99, p = 0.99, treatment 355, control 8,874, adjusted per study, RR approximated with OR.
risk of ICU admission, 17.0% lower, OR 0.83, p = 0.70, treatment 356, control 8,911, adjusted per study, RR approximated with OR.
Bliek-Bueno, 11/10/2021, retrospective, multiple countries, peer-reviewed, mean age 67.7, 15 authors, study period 4 March, 2020 - 17 April, 2020, this trial uses multiple treatments in the treatment arm (combined with Vitamin B12) - results of individual treatments may vary.
Submit Corrections or Updates.
 risk of death, 87.4% higher, OR 1.87, p < 0.001, combined, RR approximated with OR.
risk of death, 170.0% higher, OR 2.70, p < 0.001, Campania, RR approximated with OR.
risk of death, 59.0% higher, OR 1.59, p < 0.001, Aragon, RR approximated with OR.
Deschasaux-Tanguy, 11/30/2021, retrospective, France, peer-reviewed, 95 authors.
Submit Corrections or Updates.
 risk of case, 16.0% lower, OR 0.84, p = 0.02, RR approximated with OR, per standard deviation change.
Farag, 11/20/2022, Cluster Randomized Controlled Trial, Egypt, peer-reviewed, mean age 37.5, 9 authors, study period 17 May, 2020 - 30 June, 2020, trial PACTR202005599385499.
Submit Corrections or Updates.
 risk of case, 87.6% lower, RR 0.12, p < 0.001, treatment 4 of 224 (1.8%), control 20 of 139 (14.4%), NNT 7.9, 1000µg.
risk of case, 65.9% lower, RR 0.34, p = 0.005, treatment 8 of 163 (4.9%), control 20 of 139 (14.4%), NNT 11, 500µg.
Loucera, 8/16/2022, retrospective, Spain, peer-reviewed, 8 authors, study period January 2020 - November 2020.
Submit Corrections or Updates.
 risk of death, 1.5% lower, HR 0.99, p = 0.88, treatment 624, control 15,344, Cox proportional hazards, day 30.
MacFadden, 3/29/2022, retrospective, Canada, peer-reviewed, 9 authors, study period 15 January, 2020 - 31 December, 2020.
Submit Corrections or Updates.
 risk of case, no change, OR 1.00, p = 1.00, RR approximated with OR.
Meisel, 3/2/2021, retrospective, Israel, peer-reviewed, 8 authors, study period 27 January, 2020 - 23 November, 2020.
Submit Corrections or Updates.
 risk of death, 27.0% lower, OR 0.73, p = 0.54, treatment 23, control 310, RR approximated with OR.
risk of death/intubation, 6.0% lower, OR 0.94, p = 0.88, treatment 23, control 310, RR approximated with OR.
Monserrat Villatoro, 1/8/2022, retrospective, propensity score matching, Spain, peer-reviewed, 18 authors.
Submit Corrections or Updates.
 risk of death, 132.0% higher, OR 2.32, p = 0.003, RR approximated with OR.
Nimer, 2/28/2022, retrospective, Jordan, peer-reviewed, survey, 4 authors, study period March 2021 - July 2021.
Submit Corrections or Updates.
 risk of hospitalization, 27.7% lower, RR 0.72, p = 0.23, treatment 16 of 213 (7.5%), control 203 of 1,935 (10.5%), NNT 34, adjusted per study, odds ratio converted to relative risk, multivariable.
risk of severe case, 28.2% lower, RR 0.72, p = 0.16, treatment 19 of 213 (8.9%), control 241 of 1,935 (12.5%), NNT 28, adjusted per study, odds ratio converted to relative risk, multivariable.
Topless, 8/24/2022, retrospective, United Kingdom, peer-reviewed, 6 authors.
Submit Corrections or Updates.
 risk of death, 164.0% higher, OR 2.64, p < 0.001, adjusted per study, multivariable, model 2, RR approximated with OR.
risk of case, 51.0% higher, OR 1.51, p < 0.001, adjusted per study, multivariable, model 2, RR approximated with OR.
Zhang (B), 12/20/2024, retrospective, China, peer-reviewed, 3 authors, study period 3 November, 2022 - 6 January, 2023.
Submit Corrections or Updates.
 risk of case, 40.0% lower, OR 0.60, p = 0.23, treatment 566, control 34, RR approximated with OR.
Footnotes
a.
Viral infection and replication involves attachment, entry, uncoating and release, genome replication and transcription, translation and protein processing, assembly and budding, and release. Each step can be disrupted by therapeutics.
b.
When administered late in infection, HCQ may enhance viral egress by further increasing lysosomal pH beyond the effect of ORF3a's water channel activity, thereby promoting lysosomal exocytosis, inactivating degradative enzymes, and facilitating the release of SARS-CoV-2 particles into the extracellular environment140,141. Research also suggests potential cardioprotective effects at lower doses, but cardiotoxicity with excessive dosage142. Bobrowski et al. also indicate negative effects if HCQ and remdesivir are combined.
c.
Peters (B) et al. is subject to confounding by calendar-time (SOC evolved rapidly early in the pandemic, the linear covariate does not reflect non-linear SOC changes and hospital specific effects), hospital type (non-treatment hospitals were tertiary university centers), confounding by indication (4/7 hospitals initiated treatment on deterioration), immortal-time bias for as-treated (exposure assigned after baseline), significant differences for other experimental treatments, potential overadjustment from collider bias (steroid use and indication bias), limited baseline severity information, differences in hospice referral propensity across hospitals, unadjusted difference in time from onset to admission, difference in PCR positivity, and other factors. Mahévas et al. is subject to confounding by hospital (treatment highly dependent on the hospital, different SOC/ICU transfer practices, not included in PS), immortal time (only partly addressed in sensitivity analysis), co-treatment differences, calendar-time (SOC evolved rapidly early in the pandemic), binary coding for age (age ≥65 despite steep age-risk gradient), residual imbalance (variables dropped from PS), a composite outcome dependent on hospital triage/capacity, and other factors.
References