Ensitrelvir for Covid-19 Postexposure Prophylaxis
Sep 10, 2026DOI: 10.1056/nejmc2608575CorrespondenceNEJM
To the Editor: Hayden et al. (May 14/21 issue) found that ensitrelvir treatment led to a lower incidence of symptomatic Covid-19 after household exposure than placebo. We note substantial regional variation in the incidence in the placebo group: 23.0% in Japan, 3.7% in the United States, and 6.9% in other regions. As the authors indicate, these differences may result from variation in household-contact patterns, household size, circulating variants, and levels of immunity. This heterogeneity has considerable implications for postexposure prophylaxis (PEP). On the basis of the reported subgroup risks, the number needed to treat to prevent one symptomatic case was . . .
