Respiratory Syncytial Virus (RSV) is a leading cause of respiratory illness in young children. While maternal antibodies offer temporary protection in early infancy, their interaction with age-dependent disease risk remains poorly quantified. The COVID-19 pandemic, which disrupted RSV transmission, provides a unique opportunity to explore these dynamics and the potential impact of maternal vaccination. We developed a compartmental model of childhood RSV disease incorporating maternal infection history, maternally-derived immunity, waning protection in infants, and age-dependent disease risk. Calibrated to Scottish surveillance data (2016–2024), the model estimated non-linear functions for maternal immunity and RSV risk by age, and projected burden from 2024–2028 under vaccination and no-vaccination scenarios. Following pandemic-related disruption, RSV burden shifted to older children due to delayed primary exposure. Infants who missed their typical first RSV season in 2020 experienced higher disease rates at later ages, in subsequent seasons. Maternal immunity conferred protection only when infection occurred in late pregnancy, with infant protection waning to negligible levels by six months of age. Maternal vaccination at current coverage rates was projected to reduce RSV disease cases in infants ≤6 months by 15.3% (95% CI: 11.9–18.5%) in 2024–25 and 18.4% (95% CI: 12.8–23.6%) in 2025–26. Our findings highlight the role of the timing and immunological mechanisms of maternally-derived immunity in shaping RSV dynamics in young children and demonstrate how disruptions—whether through pandemic-related changes or maternal vaccination—can alter age-specific disease patterns. • Maternally-derived RSV immunity at birth was substantial only when maternal infection occurred late in pregnancy. • Maternally-derived RSV waned rapidly within the first months of life. • The probability of RSV disease upon infection declined steadily with age. • Maternal vaccination suggested a reduction in RSV disease cases among infants under 6 months of age.
Brigitta et al. (Sun,) studied this question.