Modeling Respiratory Syncytial Virus Adult Vaccination in the United States with a Dynamic Transmission Model.

BACKGROUND: Respiratory syncytial virus (RSV) is shown to cause substantial morbidity, hospitalization, and mortality in infants and older adults. Population-level modelling of RSV would allow for estimation of the full burden of disease and the potential epidemiological impact of novel prophylactics.

METHODS: We model the epidemiology of RSV in the US across all ages using a deterministic compartmental transmission model. Population-level symptomatic RSV acute respiratory tract infection (ARI) cases were projected across different natural history scenarios, both with and without vaccination of older adults aged ≥ 60. Impact of vaccine efficacy against ARIs and infectiousness and vaccine coverage on ARI incidence were assessed. Impact on medical attendance, hospitalization, complications, death and other outcomes were also derived.

RESULTS: In the absence of a vaccine, we project 17.5-22.6 million symptomatic RSV ARI cases per year in ≥18-year-olds in the US, with 3.6-4.8 million/year occurring in ≥60-year-olds. Modelling indicates that up to 2.0 million symptomatic RSV ARI cases per year could be prevented in ≥60-year-olds with a hypothetical vaccine (70% vaccine efficacy against symptomatic ARI, and 60% vaccine coverage), and up to 0.69 million cases per year can be prevented in the non-vaccinated population, assuming 50% vaccine impact on infectiousness.

CONCLUSIONS: The model provides estimated burden of RSV in the US across all age groups, with substantial burden projected specifically in older adults. Vaccination of ≥ 60 years-old population could significantly reduce the burden of disease in this population, with additional indirect effect in the < 60 years-old population due to reduced transmissibility.