Real-world data concerning the efficacy of molnupiravir in patients vaccinated against COVID-19 during the Omicron surge in Japan

Molnupiravir is among the antiviral agents used to treat COVID-19; however, reported data on the efficacy of this drug are based on results from unvaccinated patients. As such, the efficacy of molnupiravir among vaccinated patients during the B1.1.529 (Omicron) variant outbreak remains unknown. To address this issue, this study retrospectively analyzed data from 294 vaccinated patients with COVID-19 who had at least one risk factor, between May and October 2022. Patients were divided into the molnupiravir group and the control group to investigate the correlations of molnupiravir and other factors with rates of hospitalization and death (hospitalization/death) within 28 days of admission. Potential risk factors were also examined. The study findings indicated that molnupiravir was not associated with the rate of hospitalization/death, while age ≥ 80 years, residence in a long-term care facility, and presence of chronic obstructive pulmonary disease were significantly associated with the rate of hospitalization/death. Although the current results suggest that the effect of vaccination in preventing severe illness against the Omicron variant is well maintained, additional studies on risk factors and outcomes are required to validate this study’s findings.