Effective post-exposure prophylaxis of Covid-19 is associated with use of hydroxychloroquine: Prospective re-analysis of a public dataset incorporating novel data

BACKGROUND: A key trial (NCT04308668) of post-exposure prophylaxis found hydroxychloroquine-associated (HCQ) reductions of Covid-19 by 17% overall and 31% to 49% in subgroups. To understand these trends, we reanalyzed the dataset. METHODS: Our protocol conformed to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT). We compared the incidence of Covid-19 after HCQ or placebo, stratifying by intervention lag, age, and gender. RESULTS: Newly requested data missing from the dataset revealed that 52% and 19% of subjects received medication 1-2 days after intended and assumed overnight delivery or four-day intervention lag respectively. After re-analysis, we found reduced HCQ-associated incidence of Covid-19 with Early (up to 3 days post-exposure) (RR 0.58, 95%CI 0.35 -0.97; p=0.044; NNT 14.5) but not Late (RR 1.22, 95%CI 0.72 -2.04) prophylaxis. We found a significant HCQ-associated Covid-19 reduction in subjects 18 to 45 years old with Early (RR 0.54, 95%CI 0.29-0.97; p=0.0448, NNT 11.5) but not Late (RR 1.02, 95%CI 0.55-1.89) prophylaxis, attenuated in older subjects (RR 0.75, 95%CI 0-27-2.05) and by co-morbidities. Although, we did not detect effects of gender, folate, zinc, or ascorbate, confounding effects cannot be excluded. CONCLUSIONS: Using novel data and prospective re-analysis, hydroxychloroquine, in an age-dependent manner, was associated with reduced Covid-19 compatible illness when supplied for post-exposure prophylaxis between 1 and 3 days after high-or moderate-risk exposure, at higher loading and maintenance doses than in similar studies. The original study conclusions are controverted, and our finding warrants prospective confirmation.