Viral kinetics in adults with Covid-19 treated with nirmatrelvir-ritonavir or molnupiravir: a population-based, observational cohort study

BACKGROUND: This research was motivated by the widespread use of oral antivirals during the Covid-19 pandemic and the remaining uncertainty regarding their effects on viral kinetics, which have rarely been studied in real-world population cohorts of this size. METHODS: We analysed 291,340 SARS-CoV-2 cycle threshold (CT) values from 113,399 non-hospitalized adult patients in Vienna (01/2022-05/2023), including 30,451 from 12,166 nirmatrelvir-ritonavir recipients, 27,959 from 10,752 molnupiravir recipients, and 232,930 from 90,481 untreated controls. RESULTS: Both antivirals initially caused a rapid increase in mean CT values. After completion of the 5-day treatment course, CT values declined in both antiviral groups, which was not observed in untreated individuals. CONCLUSIONS: These findings provide population-level evidence on post-treatment viral kinetics of oral antivirals during the Omicron wave.