key: cord-0931236-st41fds2
authors: Neves, Fabricio S
title: Dose-response effects of hydroxychloroquine on prophylaxis against SARS-CoV-2 / COVID-19 infection
date: 2020-12-03
journal: Clin Infect Dis
DOI: 10.1093/cid/ciaa1807
sha: 46c20e4a76e75d67beaf02976a371f58eabb9c18
doc_id: 931236
cord_uid: st41fds2

nan

A c c e p t e d M a n u s c r i p t 2 Dear Editor:

The clinical trial by Rajasingham and colleagues [1] , published in Clinical Infectious Diseases, evaluated the effectiveness of using hydroxychloroquine (HDQ) 400 mg weekly or 400 mg twice weekly in preventing SARS-CoV-2 / COVID-19 infection in 1483 healthcare workers (confirmed or compatible with COVID-19: 97 cases). For the primary outcome (confirmed or compatible with COVID-19 cases), there was no significant difference between the groups treated with HDQ compared to placebo. However, Figure 2 (Kaplan Meier estimate of the time to COVID-19 compatible illness) shows the curve of the HDQ twice weekly group always higher than the curve of the HDQ weekly group. This suggests a dose-response effect: if there was no HDQ influence on the risk of developing COVID-19, a random overlap of the two curves would be expected.

It is notable that other dose-response effects can also be seen in the results of other studies about prophylactic use of HDQ against COVID-19.

In the clinical trial by Boulware and colleagues [2] , in which HDQ was tested as post-exposure prophylaxis against COVID-19 compared to placebo in 821 participants (total confirmed or compatible with COVID-19: 107 cases), there was no significant difference for the primary outcome (confirmed or compatible with COVID-19 cases). However, Table 2 

Hydroxychloroquine as pre-exposure prophylaxis for COVID-19 in healthcare workers: a randomized trial

A Randomized Trial of Hydroxychloroquine as Postexposure Prophylaxis for Covid-19

Healthcare workers & SARS-CoV-2 infection in India: A case-control investigation in the time of COVID-19