RSV Vaccination in Pregnancy

Why is RSV vaccination during pregnancy important?

Among the advances highlighted in Gavi's January vaccine outlook, maternal protection against respiratory syncytial virus, or RSV, stands out because an effective vaccine already exists. The challenge is translating that scientific achievement into protection for more newborns. Gavi's expert discussion identified wider implementation of maternal RSV vaccination as a priority, emphasizing the opportunity to prevent serious illness during the first months of life. [Gavi's vaccine outlook](https://www.gavi.org/vaccineswork/what-are-biggest-vaccine-breakthroughs-coming-2026-we-asked-six-experts)

RSV often resembles a common cold, but it can cause bronchiolitis and pneumonia in babies. WHO estimates that it causes more than 3.6 million hospitalizations and approximately 100,000 deaths annually among children younger than five worldwide. Around half of those deaths occur before six months of age. Maternal vaccination helps address this early vulnerability: antibodies produced after vaccination cross the placenta, providing temporary protection after birth. WHO's May 2025 recommendations support introducing maternal vaccination or a long-acting infant antibody product, with the choice shaped by affordability, expected coverage and delivery capacity. [WHO recommendations](https://www.who.int/news/item/30-05-2025-who-outlines-recommendations-to-protect-infants-against-rsv-respiratory-syncytial-virus)

How much protection did the maternal RSV vaccine provide?

The randomized, placebo-controlled trial published in the New England Journal of Medicine in April 2023 evaluated a bivalent prefusion F protein vaccine given during pregnancy. Its strongest findings concerned medically attended severe RSV-associated lower respiratory tract illness in infants. Estimated efficacy was 81.8% during the first 90 days and 69.4% through 180 days. These are relative reductions compared with placebo, rather than percentage-point reductions in every baby's chance of becoming ill. [Maternal RSV vaccine trial](https://www.nejm.org/doi/full/10.1056/NEJMoa2216480)

The outcome matters: these figures describe protection against a defined category of severe RSV disease, not prevention of every RSV infection, cough or hospital admission. They are estimates with statistical uncertainty, and absolute benefit depends on the underlying likelihood of severe illness. The findings support protection across early infancy without establishing complete or lifelong immunity. They also represent trial evidence published in 2023, rather than a newly announced October result. [Trial findings and definitions](https://www.nejm.org/doi/full/10.1056/NEJMoa2216480)

When should families consider vaccination or infant antibodies?

Timing recommendations differ between health systems. WHO recommends maternal RSV vaccination from 28 weeks of pregnancy, while US CDC guidance recommends Pfizer's Abrysvo from 32 weeks through 36 weeks and six days, generally during September through January in most of the continental United States. These schedules should not be treated as interchangeable instructions: local licensing, seasonal circulation and clinical guidance determine the appropriate appointment. Planning before the recommended window helps families avoid missing an opportunity for protection. [WHO timing recommendations](https://www.who.int/news/item/30-05-2025-who-outlines-recommendations-to-protect-infants-against-rsv-respiratory-syncytial-virus), [CDC pregnancy guidance](https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/pregnant-people.html)

Safety evidence also needs careful interpretation. Common reactions include injection-site pain, headache, muscle pain and nausea. Trials recorded a numerical increase in preterm births among vaccine recipients, but the difference was not statistically significant and did not establish that vaccination caused those births. Preliminary US monitoring of vaccination at 32–36 weeks did not find an increased risk of preterm birth or babies being small for gestational age. Monitoring of pregnancy outcomes, including hypertensive disorders, continues. CDC reports that the benefits within the recommended pregnancy window outweigh potential risks. [CDC safety review](https://www.cdc.gov/vaccine-safety/vaccines/rsv.html)

For babies whose mothers were not vaccinated, or when insufficient time remains for antibody transfer before delivery, a long-acting antibody injection provides another prevention pathway. Unlike a vaccine, this supplies antibodies directly. CDC lists nirsevimab and clesrovimab as infant options and states that most babies do not need both maternal vaccination and an infant antibody. The practical priority is a documented prevention plan shared between maternity and pediatric teams, taking account of vaccination history, delivery timing and local eligibility. [CDC infant protection guidance](https://www.cdc.gov/rsv/vaccines/protect-infants.html)