A Multilevel Framework for Evaluating the Impact of Monoclonal Antibodies Against Respiratory Syncytial Virus in Daycare and Households

Monoclonal antibodies (mAbs) reduce the risk of severe disease caused by respiratory syncytial virus (RSV) among immunized infants. The potential of these products to indirectly protect unimmunized contacts remains incompletely understood. This uncertainty is, in part, due to our limited understanding of how mAbs may influence population-level RSV transmission. Here, we develop a multiscale simulation framework that integrates RSV transmission dynamics across households and daycare centers to explore the characteristics of the population that could influence the strength of indirect effects of infant mAb immunization. The framework incorporates individual-level heterogeneity in age and time-varying infectiousness, as well as demographic variation in household composition and contact patterns, to capture realistic transmission pathways across close-contact networks. Using a virtual population informed by U.S. household characteristics, we show that infant immunization would only be expected to provide modest indirect protection to toddlers, and the magnitude of these effects depends on contact structure and intervention coverage. Our findings demonstrate the importance of integrating fine-scale transmission networks into evaluations of RSV prevention strategies and provide a generalizable framework for assessing population-level impacts of interventions against respiratory pathogens.