Remote post-exposure prophylaxis RCT reporting "[HCQ] did not prevent illness compatible with Covid-19 or confirmed infection when used as postexposure prophylaxis within 4 days after exposure".
However, this statement is incorrect - cases were reduced, just without statistical significance - it's not possible to conclude there was no efficacy. Additionally, treatment was not within 4 days - there was up to 68 hours shipping delay as below.
Further, 6 independent analyses of the data in this study indicate efficacy: [arxiv.org, blog.philbirnbaum.com, drive.google.com, longdom.org, medrxiv.org, osf.io, researchgate.net]
COVID-19 cases were reduced by [49%, 29%, 16%] respectively when taken within ~[70, 94, 118] hours of exposure (including shipping delay). The treatment delay-response relationship is significant at p
=0.002. For more detailed analysis, see [c19hcq.com]
See also: [nejm.org]
. Regarding the use of folic acid, see [sciencedirect.com]
Time of dosing was not recorded in these trials: [osf.io (B)]
. See [medrxiv.org (B)]
, and Pullen et al. [ncbi.nlm.nih.gov]
, which shows shipping delay for these trials of 19 - 68 hours. With enrollment up to 4 days from exposure, this implies delivery 19 - 164 hours after exposure.
Boulware et al., 3 Jun 2020, Randomized Controlled Trial, USA, peer-reviewed, 24 authors, this trial compares with another treatment - results may be better when compared to placebo.