Study of hospital health care workers showing HCQ prophylaxis reduces COVID-19 significantly, OR 0.30, p
=0.02. 94 positive health care workers with a matched sample of 87 testing negative. Full course prophylaxis was important in this study which used a low dose of 400mg/week HCQ (800mg for week 1), so it may take longer to reach therapeutic levels. Actual benefit of HCQ may be larger because severity of symptoms are not considered here but HCQ may also reduce severity.
Khurana et al., 7/24/2020, retrospective, India, South Asia, preprint, survey, 5 authors.
risk of COVID-19 case, 51.0% lower, RR 0.49, p = 0.02, treatment 6 of 22 (27.3%), control 88 of 159 (55.3%), odds ratio converted to relative risk.