National burden estimates of hospitalisations for acute lower respiratory infections due to respiratory syncytial virus in young children in 2019 among 58 countries: a modelling study.

Background: Respiratory syncytial virus (RSV) is the predominant viral pathogen associated with acute lower respiratory infection (ALRI) in children who are younger than 5 years. Little is reported on the national estimates of RSV-associated ALRI hospitalisations in these children on the basis of robust epidemiological data. We aimed to generate national level estimates for RSV-associated ALRI hospitalisations in children aged younger than 5 years.

Methods: We included data for RSV and ALRI hospitalisation in children who were younger than 5 years from systematic literature reviews (including unpublished data) and from inpatient databases, representing 58 countries. We used two different methods, the rate-based method and the proportion-based method, to estimate national RSV-associated ALRI hospitalisations in children younger than 5 years in 2019. The rate-based method synthesised data for laboratory-confirmed RSV-associated ALRI hospitalisation rates using a spatiotemporal Gaussian process meta-regression (ST-GPR). The proportion-based method applied data for RSV positive proportions among ALRI to all-cause ALRI hospitalisation envelopes (ie, total disease burden of ALRI hospitalisations of any cause) using a Bayesian regularised trimmed meta-regression (MR-BRT). Where applicable, we reported estimates by both methods to provide a plausible range for each country.

Findings: A total of 334 studies and 1985 data points (defined as an individual estimate for one age group and 1 year for each study) were included in our analysis, accounting for 398 million (59%) of the 677 million children aged younger than 5 years worldwide representing 58 countries. We reported the number of annual national RSV-associated ALRI hospitalisations for 29 countries using the rate-based method, and for 42 countries using the proportion-based method. The median number of RSV-associated ALRI hospitalisations in children younger than 5 years was 8·25 thousand (IQR 1·97-48·01), and the median rate of RSV-associated ALRI hospitalisations was 514 (339-866) hospitalisations per thousand children younger than 5 years. Despite large variation among countries, a high proportion of the RSV-associated ALRI hospitalisations were in infants aged younger than 1 year in all countries (median proportion 45%, IQR 32-56). In 272 (76%) of the 358 years included in the analysis, the RSV-associated ALRI hospitalisation rate fluctuated between 0·8 and 1·2 times the country's median yearly rate. General agreement was observed between estimates by the rate-based method and proportion-based method, with the exceptions of India, Kenya, Norway, and Philippines.

Interpretation: By incorporating data from various sources, our study provides robust estimates on national level burden of RSV-associated ALRI hospitalisation in children aged younger than 5 years. These estimates are important for informing policy for the introduction of RSV immunisations and also serve as baseline data for the RSV disease burden in young children.

Funding: The Foundation for Influenza Epidemiology.