Maternal RSVpreF Vaccine Effectiveness Against Respiratory Syncytial Virus in Hospitalized Infants
Maternal RSVpreF vaccination substantially reduced respiratory syncytial virus hospitalizations in infants through 6 months.
*Retrospective test-negative case-control study; Level 3.
Citation
Wadia U, Ong MM, Cox SN, et al. Maternal RSVpreF Vaccine Effectiveness Against Respiratory Syncytial Virus in Hospitalized Infants. JAMA Pediatrics. Published online August 17, 2026. doi:10.1001/jamapediatrics.2026.3391
Background
Respiratory syncytial virus is a leading cause of serious breathing illness and hospitalization in young infants. Australia introduced year-round maternal vaccination in 2025 to protect infants during their highest-risk first months.
Patients
1012 infants age 6 months or younger hospitalized with acute respiratory illness at 9 Australian hospitals. Infants were born from 28 weeks’ gestation. Exclusions included receipt of nirsevimab, uncertain maternal vaccine status, and, for main analyses, maternal vaccination less than 14 days before delivery.
Intervention
Maternal bivalent prefusion F respiratory syncytial virus vaccine from 28 weeks’ gestation and at least 14 days before delivery.
Control
No maternal RSVpreF vaccination.
Outcome
Hospitalization for respiratory syncytial virus lower respiratory tract disease, severe lower respiratory tract disease, and acute respiratory illness.
Follow-up Period
Birth through 6 months of infant age.
Results
| Outcome | Vaccine effectiveness |
|---|---|
| Lower respiratory tract disease hospitalization, 0-6 months | 77.8% (95% CI 66.4% to 85.3%) |
| Lower respiratory tract disease hospitalization, 0-3 months | 80.2% (95% CI 71.1% to 86.5%) |
| Lower respiratory tract disease hospitalization, 0-2 months | 86.3% (95% CI 79.0% to 91.1%) |
| Severe lower respiratory tract disease hospitalization, 0-6 months | 80.4% (95% CI 54.4% to 91.6%) |
| Acute respiratory illness hospitalization, 0-6 months | 80.8% (95% CI 70.4% to 87.6%) |
RSVpreF: prefusion F respiratory syncytial virus vaccine; CI: confidence interval.
Protection was similar by gestational age at vaccination, time from vaccination to delivery, and use near other pregnancy vaccines. Infants receiving nirsevimab were excluded, so the control group was not an active preventive treatment group.
Limitations
Observational design cannot prove causation and may have residual confounding. Results reflect hospitalized infants in Australia during the first program year. Vaccine or nirsevimab recording errors could affect estimates. Pfizer funded, sponsored, and helped design and write the study.
Funding
Pfizer; important sponsor involvement and conflict-of-interest concerns.
Clinical Application
Offer maternal RSVpreF vaccination in late pregnancy to reduce infant respiratory syncytial virus hospitalization, especially in the first 3 months.
Discussion
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In this retrospective test-negative case-control study, maternal RSVpreF vaccination was associated with lower RSV-LRTD hospitalization in infants ≤6 months (VE 77.8%, 95% CI 66.4%-85.3%). Given the observational design, how confident are you in validity and applicability before changing maternal RSV prevention practice? In this test-negative case-control study, vaccine effectiveness was calculated as (1 − adjusted odds ratio) × 100%, yielding VE 77.8% against RSV-LRTD hospitalization. Which interpretation is most appropriate?