OBJECTIVE: Norovirus (NoV) is a key cause of acute gastroenteritis (NoV-AGE), with the greatest disease burden among older adults, young children, immunocompromised individuals, and those with other underlying medical conditions. In the US, most NoV-AGE deaths occur among older adults. No vaccine for NoV is currently available, but candidates are in development. This study assesses the potential public health impact of NoV vaccination, focusing on adults aged 60+ years in the US.
METHODS: A static health-outcomes model with a decision-tree structure and a 1-year time horizon was developed for a hypothetical vaccine (65% efficacy against NoV). NoV-AGE cases (5% annual incidence among older adults) could receive NoV-related care (20% medically attended), and hospitalized cases were at risk of NoV-AGE–related mortality. Data to inform NoV-AGE incidence, resource use, and mortality were obtained from published literature, publicly available data, and clinical expert opinion, and were calibrated to ensure estimated annual NoV-AGE incidence, resource use, and deaths align with high-quality publications. Health outcomes included annual NoV-AGE cases, hospitalizations, deaths, and number needed to vaccinate to prevent 1 NoV-AGE case or 1 hospitalization. Sensitivity analyses were conducted to assess the impact of parameter uncertainty and modeling assumptions.
RESULTS: The model estimated that among adults aged 60+ years in the US, vaccination with 50% coverage may prevent 1,290,188 NoV-AGE cases (percentage reduction: 32.5%), 258,038 medically-attended NoV-AGE cases, 17,289 NoV-AGE hospitalizations, and 375 NoV-AGE–related deaths annually. To prevent 1 NoV-AGE case or 1 hospitalization, 62 or 4,592 older adults need to be vaccinated, respectively. Sensitivity analysis showed results to be robust when varying key parameters (NoV-AGE incidence, vaccine coverage, vaccine efficacy).
CONCLUSIONS: NoV vaccination may provide significant public health benefits for older adults in the US. Estimates should be refined with updated epidemiological and clinical data as NoV surveillance improves and vaccine development continues.
