Double-zero-event studies matter: a re-evaluation of physical distancing, face masks, and eye protection for preventing person-to-person transmission of COVID-19 and its policy impact

In a recent timely systematic review, Chu et al. (Chu et al., 2020) assessed the effectiveness of face masks, eye protection, and physical distancing for preventing COVID-19. Because the sample sizes are not large, especially in some studies of COVID-19, this review contains a considerable number of studies with zero counts of infection events, creating challenges in estimating effect sizes. If zero counts appear in both groups, this double-zero-event study (DZS) is omitted from the analyses, as implied in the forest plots in Chu et al.

Source: Journal of Clinical Epidemiology - February 1, 2021 Category: Epidemiology Authors: Mengli Xiao, Lifeng Lin, James S. Hodges, Chang Xu, Haitao Chu Tags: Letter to the editor Source Type: research