Efficacy and safety of maternal RSV vaccination against infant lower respiratory tract infections: a systematic review and meta-analysis

Why clinicians should know about it

• Picked for Pediatrics and Child Health (paper of the day, 5 October 2026): Maternal RSV vaccine efficacy for infant LRTI

Abstract

BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of infant lower respiratory tract infection (LRTI) and hospitalisation worldwide. Maternal RSV prefusion F (RSVpreF) vaccination protects infants through transplacental antibody transfer. We aimed to synthesise the efficacy, real-world effectiveness, and safety of maternal RSV vaccination for preventing infant LRTI, integrating randomised and observational evidence. METHODS: We searched PubMed, Embase, Scopus, and Cochrane CENTRAL (to June 2026) for randomised controlled trials (RCTs) and observational studies of maternal RSV vaccination reporting infant LRTI, hospitalisation, or maternal-infant safety. A single reviewer, with large language model-assisted verification, screened records, extracted data, and assessed risk of bias (RoB 2; Newcastle-Ottawa Scale). Randomised and observational evidence were pooled separately using random-effects models; overlapping populations were resolved based on study periods and named participating sites. Certainty was rated with GRADE (PROSPERO CRD420261400053). RESULTS: Twenty-four studies (9 RCTs enrolling approximately 18,600 pregnant women, 15 observational) were included; all 15 observational studies evaluated the licensed Pfizer vaccine (Abrysvo). Pooled vaccine effectiveness against infant RSV-associated hospitalisation was 79.7% (95% CI 73.9-84.2) within 3 months and 68.1% (57.1-76.3) through 6 months. Randomised efficacy against severe RSV-LRTI was 70% for the licensed Pfizer vaccine, closely concordant with the real-world effectiveness; efficacy against medically attended RSV-LRTI was 51.5% (36.3-63.1). Preterm birth was modestly increased in the randomised trials (Mantel-Haenszel RR 1.17, 95% CI 1.03-1.32), but the signal was not robust: it became non-significant after excluding the GSK trial (GRACE; 1.10, 0.95-1.27), and for the licensed Pfizer vaccine, the increase was small and not robustly significant (pivotal MATISSE trial 1.20, 0.98-1.46; three-trial Pfizer pool 1.21, 1.00-1.46), while observational data showed a biologically implausible protective association (0.90, 0.82-0.99), consistent with healthy vaccinee confounding. No other maternal or neonatal safety signal was identified. Certainty of evidence was moderate for effectiveness and efficacy. CONCLUSION: Maternal RSVpreF vaccination confers substantial, generalisable protection against infant RSV disease, with randomised and real-world evidence in close agreement. For the licensed Pfizer vaccine administered within its approved 32-36-week window, no robustly significant increase in preterm birth is established, supporting its continued programmatic use alongside ongoing post-marketing surveillance. SYSTEMATIC REVIEW REGISTRATION: Unique Identifier: CRD420261400053 https://www.crd.york.ac.uk/PROSPERO/view/CRD420261400053.

Abstract as published, via PubMed.