Infant RSV hospitalisations fell by a quarter to nearly half in one season

Two products prevent RSV hospitalisation in infants: a **maternal RSV
vaccine** given in pregnancy, and nirsevimab, a long-acting monoclonal
antibody given to the baby. Both became **widely available in the United
States during the 2024–25 RSV season** — the first season in which they were.

The result

Comparing **RSV-associated hospitalisation rates among infants aged 0–7
months** in 2024–25 against pre-COVID-19 pandemic RSV seasons, in **two
surveillance networks**:

Two independent networks, both showing a substantial fall, in the first season
the products were available at scale.

Why "ecologic" matters

This is an ecologic analysis — it compares population rates between
seasons, not vaccinated infants against unvaccinated ones. It cannot on its own
prove the products caused the drop, and honest reporting says so.

What it can do is answer the question that matters for planning: **did the
number of babies in hospital with RSV actually go down after these products
were introduced.** It did, in both networks.

The practical conclusion

**Effective health care planning is needed to protect infants as early in
the RSV season as possible**, through **maternal vaccination during
pregnancy** or infant receipt of nirsevimab.

"As early in the season as possible" is the operational point. RSV season
arrives on a schedule; a baby born into the middle of it who receives
nirsevimab in week three has already been exposed. The protection has to be in
place before, which means the decision is made during pregnancy or in the
first days of life — not when the season is under way.

*Source: Patton ME, Moline HL, Whitaker M, et al. Interim Evaluation of
Respiratory Syncytial Virus Hospitalization Rates Among Infants and Young
Children After Introduction of Respiratory Syncytial Virus Prevention Products
— United States, October 2024–February 2025. MMWR, Centers for Disease Control
and Prevention.*