Hydroxychloroquine reduces COVID-19 risk: real-time meta analysis of 423 studies

Covid Analysis, Mar 2025

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https://c19hcq.org/cahcq.html

HCQ for COVID-19

1st treatment shown to reduce risk in March 2020, now with p < 0.00000000001 from 423 studies, used in 59 countries.

Lower risk for mortality, hospitalization, progression, recovery, cases, and viral clearance.

No treatment is 100% effective. Protocols combine treatments.

5,700+ studies for 135 treatments. c19hcq.org

Early treatment shows 66% [54‑74%] lower risk with pooled effects in 38 studies. Results are similar for higher quality studies and for peer-reviewed studies. The 17 mortality and 16 hospitalization results show 76% [61‑85%] lower mortality and 41% [28‑51%] lower hospitalization.

Late treatment is less successful, with 22% [18‑26%] lower risk from 273 studies. Very late treatment may be harmful, especially with excessive dosages.

Randomized Controlled Trials show 21% [8‑32%] lower risk, or 30% [18‑41%] when excluding late treatment.

Control HCQ

There is substantial bias towards publishing negative results. Prospective studies show higher efficacy. Negative RCTs received priority treatment at top journals, while positive trials report difficulty publishing. There is a strong geographical bias, with significantly more negative studies from North America.

Results are missing for 51% of early treatment and prophylaxis RCTs, compared to 18% for late treatment, consistent with the higher prevalence of positive studies for early treatment and prophylaxis, and bias against publishing positive results.

No treatment is 100% effective. Protocols combine safe and effective options with individual risk/benefit analysis and monitoring. Other treatments are more effective. Lung pharmacokinetics show high inter-individual variability1.

All data and sources to reproduce this analysis are in the appendix.

Multiple other meta analyses show efficacy for early treatment or prophylaxis2-9.

9 meta analyses show significant improvements with hydroxychloroquine for mortality1-4, hospitalization1, recovery5, combined death/hospitalization/cases6, cases7,8, and viral clearance9.

Important missing comments or errors? Let us know.

1. Landsteiner de Sampaio Amêndola et al., COVID-19 Infection in Rheumatic Patients on Chronic Antimalarial Drugs: A Systematic Review and Meta-Analysis, Journal of Clinical Medicine, doi:10.3390/jcm11226865.mdpi.com, doi.org.

2. Risch, H., Early Outpatient Treatment of Symptomatic, High-Risk Covid-19 Patients that Should be Ramped-Up Immediately as Key to the Pandemic Crisis, American Journal of Epidemiology, kwaa093, 27 May 2020, doi:10.1093/aje/kwaa093.oup.com, doi.org.

3. Risch (B), H., Response to: “Early Outpatient Treatment of Symptomatic, High-Risk Covid-19 Patients” and “Re: Early Outpatient Treatment of Symptomatic, High-Risk Covid-19 Patients that Should be Ramped-Up Immediately as Key to the Pandemic Crisis”, American Journal of Epidemiology, July 20, 2020, doi:10.1093/aje/kwaa152.oup.com, doi.org.

4. Stricker et al., Hydroxychloroquine Pre-Exposure Prophylaxis for COVID-19 in Healthcare Workers from India: A Meta-Analysis, Journal of Infection and Public Health, doi:10.1016/j.jiph.2021.08.001.sciencedirect.com, doi.org.

5. Prodromos et al., Hydroxychloroquine is effective, and consistently so used early, for Covid-19: A systematic review, New Microbes and New Infections, doi:10.1016/j.nmni.2020.100776.sciencedirect.com, doi.org.

6. Ladapo et al., Randomized Controlled Trials of Early Ambulatory Hydroxychloroquine in the Prevention of COVID-19 Infection, Hospitalization, and Death: Meta-Analysis, medRxiv, doi:10.1101/2020.09.30.20204693.medrxiv.org, doi.org.

7. García-Albéniz et al., Systematic review and meta-analysis of randomized trials of hydroxychloroquine for the prevention of COVID-19, European Journal of Epidemiology, doi:10.1007/s10654-022-00891-4.springer.com, doi.org.

8. Han et al., The efficacy and safety of hydroxychloroquine for COVID-19 prophylaxis and clinical assessment: an updated meta-analysis of randomized trials, Journal of Thoracic Disease, doi:10.21037/jtd-23-1043.amegroups.com, doi.org.

9. Brouqui et al., SARS-CoV 2 Viral Clearance in 1276 Patients: Associated Factors and the Role of Treatment with Hydroxychloroquine and Azithromycin, Acta Scientific Microbiology, doi:10.31080/ASMI.2024.07.1413.actascientific.com, doi.org.

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Please send us corrections, updates, or comments. c19early involves the extraction of 100,000+ datapoints from thousands of papers. Community updates help ensure high accuracy. Treatments and other interventions are complementary. All practical, effective, and safe means should be used based on risk/benefit analysis. No treatment or intervention is 100% available and effective for all current and future variants. We do not provide medical advice. Before taking any medication, consult a qualified physician who can provide personalized advice and details of risks and benefits based on your medical history and situation. IMA and WCH provide treatment protocols.

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