ACOG extends the pregnancy RSV shot window through March 1 — what changed this week

The most useful infant-health development this week is not another birth-story headline. It is a practical change to when pregnant people in most of the continental United States can get the maternal RSV vaccine.

## Background

RSV is the leading cause of hospitalization among infants in the United States. Two tools now sit side by side:

1. **Maternal vaccine (Pfizer Abrysvo)** — one dose at 32 weeks 0 days through 36 weeks 6 days. Antibodies cross the placenta and protect most babies through the first RSV season.
2. **Infant monoclonal antibody (nirsevimab, and in some settings clesrovimab)** — given to the baby after birth. Used when the parent was not vaccinated this pregnancy, when birth is planned within two weeks of a possible shot, or in a later pregnancy after Abrysvo was already given.

ACOG still recommends Abrysvo only in the first eligible pregnancy. Repeat maternal doses are not indicated. Only Abrysvo is licensed for pregnancy; other adult RSV shots must not be substituted.

## What changed

ACOG’s maternal immunization schedule addendum (2 September 2026) and the updated practice advisory stretch the seasonal window from **September through 1 January** to **September 1 through March 1**.

Why: RSV used to peak from October through March. Recent seasons have slid later. The 2025–2026 season peaked in March and kept circulating into May. A January cutoff left late-winter births uncovered.

Alaska and tropical jurisdictions should still follow local seasonality, not the continental calendar.

## Competing viewpoints

- **Vaccinate in pregnancy when eligible.** One fewer injection for the newborn; protection starts at birth. ACOG cites roughly 8 in 10 babies protected from serious RSV illness and about 7 in 10 protected from a hospital stay in the first six months.
- **Prefer the infant antibody.** Some clinicians and parents choose nirsevimab when supply is reliable, when gestational age will miss the 32–36 week window, or when the parent already received Abrysvo in a prior pregnancy.
- **Coverage and logistics.** A longer window only helps if clinics stock Abrysvo into late winter and insurers treat March doses as in-season. That is an operations problem, not a science problem.

Co-administration with other recommended pregnancy vaccines remains acceptable.

## What to watch next

- Whether your prenatal clinic will book Abrysvo visits after January.
- Infant-antibody supply for babies born after a parent who already had Abrysvo.
- Local public-health calendars in Alaska and tropical regions.
- Any CDC season update if spring circulation stretches again.

This is education, not personal medical advice. Timing depends on gestational age, planned delivery date, prior RSV vaccination, and local seasonality. Ask the clinician who will be in the room at birth.

Sources: ACOG maternal immunization schedule addendum (2 September 2026); ACOG practice advisory on maternal RSV vaccination (updated August 2026); ACOG patient FAQ “The RSV Vaccine and Pregnancy” (updated September 2026).