•HCQ is effective for COVID-19. The probability that an ineffective treatment generated results as positive as the 121 studies to date is estimated to be 1 in 27 million (p = 0.000000037).
•Early treatment is most successful, with 100% of studies reporting a positive effect and an estimated reduction of 63% in the effect measured (death, hospitalization, etc.) using a random effects meta-analysis, RR 0.37 [0.29-0.48].
•100% of Randomized Controlled Trials (RCTs) for early, PrEP, or PEP treatment report positive effects, the probability of this happening for an ineffective treatment is 0.002.
•There is evidence of bias towards publishing negative results. Significantly more retrospective studies report negative results compared to prospective studies, p = 0.04.
•Significantly more studies in North America report negative results compared to the rest of the world, p = 0.003.
