Estimating the impact of vaccination and long-acting monoclonal antibodies for RSV epidemics across Hong Kong, Beijing, and Thailand: a modelling study

BackgroundRespiratory syncytial virus (RSV) is a major cause of acute lower respiratory infections worldwide, with high morbidity among infants and older adults. Recent approvals of long-acting monoclonal antibodies (mAbs) and vaccines offer new prevention opportunities, but their impact in Asian settings remains uncertain. MethodsWe developed age-structured SEIR transmission models for Hong Kong, Beijing, and Thailand, calibrated to region-specific surveillance and seroprevalence data from 2014-2019. Using Bayesian inference, we estimated RSV transmission dynamics and simulated intervention scenarios involving long-acting mAbs for high-risk infants, maternal vaccination, and older adult vaccination. FindingsRSV showed distinct seasonality: year-round in Hong Kong, winter peaks in Beijing, and rainy-season peaks in Thailand. Estimated annual infection attack rates among infants <1 year were 51.1% in Hong Kong and 22.5% in Beijing, and 75.8% and 70.1% among children aged 1-4 years, compared with 27.9% among 0-4 years in Thailand. Simulations suggest long-acting mAbs and maternal vaccination (coverage 38.5%) could avert 15.6-19.5% and 18.0-25.2% of severe infant outcomes, respectively. Vaccination of older adults (coverage 30-40%) reduced RSV-associated outcomes by 21.7-27.7% in Hong Kong, 33.9-39.7% in Beijing and 34.8-49.8% in Thailand. Combined interventions achieved reductions of 39.2% (27.5-55.8), 49.4% (42.0-59.7), and 53.8% (44.1-64.8) in severe outcomes among infants <1 year, 19.3% (18.9-21.7), 27.7% (26.9-31.5) and 31.5% (31.3-33.9) among 60-74 years, 26.5% (26.2-28.7), 52.3% (51.5-54.8) and 37.8% (37.6-40.0) among [&ge;]75 years, in Hong Kong, Beijing, and Thailand, respectively. InterpretationOur modelling framework provides a novel approach to evaluate RSV prevention strategies in Asian populations with diverse seasonality. As real-world effectiveness data emerge, future research should refine estimates and optimise intervention combinations for maximum public health impact. FundingMSD Investigator Studies Program, General Research Fund, Health and Medical Research Fund. (Word count: 298) Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWe searched PubMed and Google Scholar for studies published before October 2025 using terms such as "RSV transmission model," "RSV monoclonal antibodies," "RSV maternal vaccination," and "older adult RSV vaccine." Most modelling studies focused on high-income countries in temperate regions, including Europe, the United States, and Australia. These studies evaluated the impact of RSV immunization strategies but did not address populations with diverse seasonality patterns or those in low- and middle-income countries. Evidence on RSV burden in Asia remains limited, and few studies have integrated seroprevalence data with transmission modelling to inform intervention strategies. Added value of this studyThis study provides the first comparative modelling analysis of RSV transmission dynamics and intervention impacts across three Asian settings--Hong Kong, Beijing, and Thailand-- representing subtropical, temperate, and tropical climates. By calibrating age-structured SEIR models to local surveillance and seroprevalence data, we estimated infection attack rates and assessed the potential benefits of long-acting monoclonal antibodies, maternal vaccination, and older adult vaccination. Our findings show that moderate uptake of RSV interventions can substantially reduce severe outcomes and reinforce the need for implementing comprehensive prevention strategies in Asian settings. Implications of all the available evidenceOur modelling framework offers a practical tool for policymakers to evaluate intervention combinations and prioritise resource allocation. As real-world effectiveness and uptake data become available, these insights can guide optimisation of RSV prevention programmes across diverse settings.