Clinical Outcomes of Early Antiviral Treatment for COVID-19 in a Japanese Long-Term Care Facility With Limited Resources: A Retrospective Study of 107 Residents

Background After COVID-19 was reclassified as a Class 5 infectious disease in Japan on May 8, 2023, long-term care facilities assumed primary responsibility for onsite management of infected residents. Detailed reports of clinical outcomes under this policy are scarce. SARS-CoV-2 infection remained clinically relevant despite repeated vaccination, including receipt of five or more vaccine doses in many residents, highlighting the need for early antiviral treatment in nursing home settings. Methods We conducted a retrospective observational study from May 8, 2023, to February 28, 2025, in a resource-limited Japanese long-term care facility. Among 113 residents diagnosed with COVID-19, six presented with moderate illness at diagnosis, operationally defined as decreased oxygen saturation with SpO₂ ≤ 93%, and were immediately referred to and admitted to the hospital. These residents were excluded from the primary analysis. The primary cohort comprised 107 residents with mild illness at diagnosis who received molnupiravir 800 mg twice daily for five days within eight hours of diagnosis. Outcomes included clinical progression, hospitalization after initiation of molnupiravir, mortality, and outbreak characteristics. Results Among the 107 treated residents, 104 were wheelchair-dependent, and three were bedridden. The mean age was 85.6 years, and 49 residents were aged ≥85 years. Prior COVID-19 vaccination was documented in 95 residents (88.7%). Eighty-three residents (77.5%) had documented receipt of at least five vaccine doses, whereas 24 residents (22.4%) had no documented receipt of at least five doses, including residents with zero to four recorded doses and those with unknown vaccination history. One resident (0.9%) deteriorated on day 3 despite early antiviral treatment, was hospitalized, and died after hospitalization. No in-facility deaths occurred. Six outbreak clusters were identified during the study period. Conclusions Early antiviral treatment for mild COVID-19 was feasible and associated with favorable outcomes in a resource-limited long-term care facility despite severe structural limitations, including multi-bedrooms and poor ventilation. These findings support rapid diagnosis, prompt molnupiravir initiation, and early hospital referral for residents with oxygen desaturation in frail older adults living in long-term care facilities.