HCQ and CQ as COVID19 Chemoprevention

The multinational COPCOV double blind placebo controlled RCT (n = 4,652) conducted between April 2020 and March 2022 among unvaccinated healthy, nonpregnant, adults between 17 and 70 years of age recruited in 11 different countries found that HCQ/CQ reduced the incidence of PCR confirmed symptomatic COVID19 by 57% and the incidence of lab confirmed symptomatic COVID19 by 15% over a 3 month follow up period. Administration of 155 mg daily of HCQ/CQ after a 10 mg/kg baseline dose also reduced all cause respiratory illness by 39% and the mean number of workdays lost per 1,000 participants by 104 days and the incidence of SAEs by almost half.

Although most RCTs that set out to examine the effectiveness of CQ or HCQ in mitigating COVID19 disease were severely underpowered or stopped before completion due to a lack of participant retention, two other RCTs found that prophylactic doses of HCQ/CQ reduced the incidence of COVID19 disease. An open-label, parallel RCT conducted among young healthy migrant workers living in residential dormitories in Singapore for 42 days (n = 3037) found that ‘the frequency of SARS-CoV-2 infection was significantly lower in participants receiving hydroxychloroquine (212 out of 432 participants, 49%) and povidone-iodine throat spray (338 out of 735 participants, 46%), compared with vitamin C (433 out of 619 participants, 70%).’ HCQ and povidone iodine spray reduced the absolute risk of SARS-COV-2 infection by 21% and 24% respectively compared to vitamin C and remained statistically significant even after adjusting for confounding. A multicenter open label RCT conducted among Iranian healthcare workers between August 11, 2020 and November 11, 2020 (n = 146) found that administration of 400 mg HCQ over 12 weeks reduced the incidence of symptomatic COVID19 by nearly half over 12 weeks and incidence of severe COVID19 symptoms (n = 6) by 100% compared to the control group.