Effectiveness of maternal vaccines and long-acting monoclonal antibodies against respiratory syncytial virus disease burden in early life: a scoping review of dynamic modelling studies

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of respiratory illness and hospitalisation in young children. New interventions for preventing severe RSV in early life, namely a maternal vaccine and a long-acting monoclonal antibody, have recently been approved and are available for use. Mathematical models of RSV transmission have been used to predict the impact of novel interventions, in anticipation of product licensure, and to model the impact of interventions once available. However, models vary in structure, parameterisation, assumptions, and scenarios simulated. METHODS: In this scoping review, we surveyed dynamic modelling studies estimating the prospective population-level impact of an RSV maternal vaccine or a long-acting monoclonal antibody in children <2 years, focussing on upper-middle- and high-income settings. We extracted data on model structures, assumptions, and parameterisation, and synthesised the estimates of immunisation impact across studies. FINDINGS: Of the 210 articles reviewed, seven met our criteria. Two studies modelled only a maternal vaccination strategy, one modelled a long-acting monoclonal strategy, and four modelled both. Across the year-round and seasonal strategies modelled, estimates ranged from 5 to 21 and 11 to 32 annual RSV hospitalisations per 1,000 children averted for a maternal vaccine and a monoclonal antibody respectively in infants aged <3 months, corresponding to approximately 10-53 % and 32-70 % hospitalisations averted. Six of the studies explicitly captured natural maternally-derived immunity in infants, but the magnitude and duration varied widely. INTERPRETATION: All studies found that either a maternal vaccine and/or a long-acting monoclonal antibody could significantly reduce RSV hospitalisations in children younger than 12 months. We identified broad consistency in results across studies, and all studies captured declining impact in older children. Predicted impact was larger for a monoclonal antibody compared to a vaccine, due to higher assumed coverage and efficacy. Assumptions around maternal immunity varied, and improving the evidence base for this mechanism would be beneficial.