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HCQ study #194 of 260
11/21 Pre-Exposure Prophylaxis study (treated before exposed to the virus)
Revollo et al., Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkaa477 (Peer Reviewed)
Hydroxychloroquine pre-exposure prophylaxis for COVID-19 in healthcare workers
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Retrospective PrEP analysis with 69 healthcare workers on PrEP HCQ, and 418 control.
Authors report PCR and IgG results, with no baseline results for either. Authors note they "identified 69 HCWs receiving HCQ" while providing no information as to why or when they started HCQ.
No conclusions can be drawn from this study because many workers may have been positive before starting HCQ. Only 14% of workers chose to use HCQ and they may have been motivated to do so because they had an infection.
Authors perform several different adjustments, finding very different results. No information on death, hospitalization, symptoms, or severity is provided. Details on timing of serology and baseline serology status is not provided. Potential bias due to self-selection for risk.
25% of infections were detected before 7 days, indicating that they actually happened earlier (PCR false positive is very high initially). It is likely that many infections were before HCQ could reach therapeutic levels.


Revollo et al., 11/21/2020, retrospective, Spain, Europe, peer-reviewed, 16 authors.
risk of COVID-19 case, 23.0% lower, RR 0.77, p = 0.52, treatment 16 of 69 (23.2%), control 65 of 418 (15.6%), adjusted per study, PSM risk of PCR+.
risk of COVID-19 case, 43.0% higher, RR 1.43, p = 0.42, treatment 17 of 60 (28.3%), control 62 of 404 (15.3%), adjusted per study, PSM risk of IgG+.

Effect extraction follows pre-specified rules prioritizing more serious outcomes. For an individual study the most serious outcome may have a smaller number of events and lower statistical signficance, however this provides the strongest evidence for the most serious outcomes when combining the results of many trials.
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