Design: Test-negative case-control study in 9 hospitals, first programme year
Population: 655 Australian infants up to 6 months admitted with lower respiratory tract disease
Primary outcome: RSV lower respiratory tract disease hospitalisation
Effect: VE 77.8% (95% CI 66.4% to 85.3%) to 6 months; 86.3% to 2 months

Australia added the RSVpreF vaccine to its national programme in February 2025 for pregnant women from 28 weeks' gestation, year-round. This test-negative case-control study covered nine hospitals with year-round testing, comparing infants up to six months admitted with RSV lower respiratory tract disease against infants admitted with RSV-negative respiratory illness, from March 2025 to February 2026.

Of 655 infants with lower respiratory disease, 30% of RSV-positive cases and 64% of RSV-negative controls had vaccinated mothers. Vaccine effectiveness against RSV hospitalisation was 77.8% (95% CI 66.4% to 85.3%) up to six months, 86.3% up to two months, and 68.2% between two and four months. Protection against severe disease was similar (80.4%). Effectiveness held regardless of when in pregnancy the vaccine was given or how close to delivery.

The youngest infants, who make up most RSV admissions, gained most. This is real-world confirmation of trial results in a routine programme. In India, RSV is a leading cause of infant admission; the vaccine's regulatory status and availability here should be checked locally before advising patients.

Discuss maternal RSV vaccination with pregnant women from 28 weeks where it is available.
Expect the strongest protection in the first two to three months of life.
Confirm the mother's vaccination status when an infant presents with bronchiolitis.
Check local availability and recommendations; Indian regulatory status is not established here.

Why it matters

Most RSV admissions are in the first months of life, exactly where this protection is strongest.

The statistics, in plain English

In a test-negative design, infants who tested positive are compared with those who tested negative for the same symptoms; vaccine effectiveness is one minus the odds ratio of vaccination. 77.8% means vaccinated mothers' babies had about a fifth of the odds of RSV admission. Effectiveness fell to 68% after two months, with a wider interval, as maternal antibodies wane.