Age distribution of respiratory syncytial virus disease in children younger than 5 years in low-income and middle-income countries: a systematic review and meta-analysis

BACKGROUND: Low-income and middle-income countries (LMICs) bear the greatest burden of respiratory syncytial virus (RSV) disease. WHO recommends passive immunisation to protect infants younger than 6 months and, in some strategies, infants up to age 12 months, but detailed age data are needed to determine optimal timing and impact. Our study estimates age distributions for the full range of RSV outcomes among children younger than 5 years in LMICs. METHODS: We conducted a systematic review and meta-analysis of RSV age distributions for seven health or health-care outcomes (hereafter, RSV outcomes): community cases, outpatient or clinic visits, emergency room visits, inpatient ward admissions, intensive care unit (ICU) admissions, facility deaths, and non-facility deaths. Inclusion required at least 30 laboratory-confirmed counts of RSV disease in children younger than 5 years, for a single RSV outcome from a single LMIC in the pre-COVID-19 decade (Jan 1, 2010, to Dec 31, 2019). We invited authors of included studies to share RSV counts by week or month of age. Using a Bayesian hierarchical model, we fitted parametric age distributions (by week for children