# A retrospective cohort study and spatial analysis of climate and community-level determinants of respiratory syncytial virus notifications among Queensland infants, prior to the introduction of the RSV mother and infant protection program (RSV-MIPP) immunisation initiative

## TL;DR

This study examines RSV infection rates in Queensland infants before a new immunization program, finding higher rates in certain climates and family sizes.

## Contribution

The study provides baseline RSV incidence data and identifies climate and community-level factors influencing RSV notifications in infants.

## Key findings

- RSV incidence was higher in temperate and arid/semi-arid climates compared to tropical climates.
- Larger family sizes were associated with increased RSV incidence.
- Remote areas had lower RSV incidence, possibly due to undertesting or lower case detection.

## Abstract

Respiratory syncytial virus (RSV) is a highly infectious seasonal respiratory pathogen and a major cause of morbidity in young children. In Australia, RSV is the leading cause of hospitalisation for bronchiolitis and pneumonia among children aged < 2 years, with the highest severity observed in infants aged < 6 months. RSV became a nationally notifiable condition in July 2021, and the national RSV Mother and Infant Protection Program (RSV-MIPP) commenced in February 2024. Baseline data on RSV incidence and its determinants are needed to evaluate the effectiveness of the program and identify populations at greatest risk.

Retrospective cohort study with spatial analysis of all RSV notifications among children aged < 2 years residing in the state of Queensland, Australia between 1 January 2022 and 31 December 2023. Data were obtained from the Queensland Notifiable Conditions System. Incidence rates were calculated by exact age in infant months, year, epidemiological week, and climate zone, using all resident children as the denominator population. Spatial cluster analysis methods identified postcode areas with high incidence, and associations in climate zones, and community-level characteristics (remoteness, socioeconomic status, average number of children per family household).

18,683 notifications were recorded among children aged < 2 years between 2022−2023 (79.7 per 1,000 in 2022; 84.8 per 1,000 in 2023). Incidence was consistently higher among 1-month-olds (96.6 per 1,000) and 12-month-olds (96.7 per 1,000). Compared to tropical climates, incidence was higher in temperate (aRR 1.26, 95% CI 1.13−1.41) and arid/semi-arid zones (aRR 1.18, 95% CI 1.00−1.38), with differences in timing and magnitude of epidemics between climate zones. Higher incidence was observed in areas with larger family sizes (aRR 1.39, 95% CI 1.13−1.72). Remoteness was associated with lower incidence (aRR 0.89, 95% CI 0.87−0.92).

In Queensland, children living in areas with larger family sizes and temperate or arid/semi-arid climates experienced higher incidence of RSV infections. Lower recorded incidence in remote areas may reflect undertesting or lower-case ascertainment. Future RSV-MIPP strategies should prioritise climatic and community-level determinants through targeted outreach and enhanced surveillance to facilitate equitable access. There is an urgent need for new strategies to protect infants aged > 6 months, when protection from maternal vaccination and birth dose therapeutics wanes.

The online version contains supplementary material available at 10.1186/s12889-026-26288-6.