Prophylaxis against covid-19: living systematic review and network meta-analysis

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Updates</jats:title> <jats:p>This is the second version (first update) of the living systematic review, replacing the previous version (available as a data supplement). When citing this paper please consider adding the version number and date of access for clarity.</jats:p> </jats:sec> <jats:sec> <jats:title>Objective</jats:title> <jats:p>To determine and compare the effects of drug prophylaxis on severe acute respiratory syndrome coronavirus virus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (covid-19).</jats:p> </jats:sec> <jats:sec> <jats:title>Design</jats:title> <jats:p>Living systematic review and network meta-analysis (NMA).</jats:p> </jats:sec> <jats:sec> <jats:title>Data sources</jats:title> <jats:p>WHO covid-19 database, a comprehensive multilingual source of global covid-19 literature to 4 March 2022.</jats:p> </jats:sec> <jats:sec> <jats:title>Study selection</jats:title> <jats:p>Randomised trials in which people at risk of covid-19 were allocated to prophylaxis or no prophylaxis (standard care or placebo). Pairs of reviewers independently screened potentially eligible articles.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>After duplicate data abstraction, we conducted random-effects bayesian network meta-analysis. We assessed risk of bias of the included studies using a modification of the Cochrane risk of bias 2.0 tool and assessed the certainty of the evidence using the grading of recommendations assessment, development and evaluation (GRADE) approach.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The second iteration of this living NMA includes 32 randomised trials which enrolled 25 147 participants and addressed 21 different prophylactic drugs; adding 21 trials (66%), 18 162 participants (75%) and 16 (76%) prophylactic drugs. Of the 16 prophylactic drugs analysed, none provided convincing evidence of a reduction in the risk of laboratory confirmed SARS-CoV-2 infection. For admission to hospital and mortality outcomes, no prophylactic drug proved different than standard care or placebo. Hydroxychloroquine and vitamin C combined with zinc probably increase the risk of adverse effects leading to drug discontinuation—risk difference for hydroxychloroquine (RD) 6 more per 1000 (95% credible interval (CrI) 2 more to 10 more); for vitamin C combined with zinc, RD 69 more per 1000 (47 more to 90 more), moderate certainty evidence.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Much of the evidence remains very low certainty and we therefore anticipate future studies evaluating drugs for prophylaxis may change the results for SARS-CoV-2 infection, admission to hospital and mortality outcomes. Both hydroxychloroquine and vitamin C combined with zinc probably increase adverse effects.</jats:p> </jats:sec> <jats:sec> <jats:title>Systematic review registration</jats:title> <jats:p>This review was not registered. The protocol established a priori is included as a supplement.</jats:p> </jats:sec> <jats:sec> <jats:title>Funding</jats:title> <jats:p>This study was supported by the Canadian Institutes of Health Research (grant CIHR-IRSC:0579001321).</jats:p> </jats:sec>