Maternal RSV vaccine (Abrysvo) in pregnancy

One of the most effective ways to protect a newborn from RSV in their first months of life is to vaccinate the mother before delivery. Antibodies made by the mother's immune system cross the placenta and are present in the baby's blood at birth — a strategy that has been used successfully with whooping cough (Tdap) for years, now extended to RSV.

What is Abrysvo?

Abrysvo is Pfizer's RSV vaccine, FDA-approved for two distinct uses:

• Pregnant people at 32–36 weeks gestation — to protect the newborn through maternal antibody transfer
• Adults 60 and older — to directly protect older adults from RSV lower respiratory disease

It is a protein subunit vaccine — it works by presenting pieces of the RSV protein to the immune system, prompting it to generate antibodies. Those antibodies cross the placenta in the third trimester, so the baby is born with RSV-specific protection already in place.

The 32–36 week window

The timing window is deliberate. After 32 weeks, the placenta transfers maternal antibodies at a high rate — giving enough time for levels to build in the baby before delivery. Waiting until after 36 weeks risks not generating high enough antibody levels in the baby by the time of birth.

If you're in that window and RSV season is approaching (or currently active), this is the time to ask your OB.

How it fits with Beyfortus

Abrysvo (maternal vaccine) and Beyfortus (infant monoclonal antibody) are both protective — but they work differently and serve as alternatives or complements depending on your timeline:

• If the mother received Abrysvo during pregnancy, the CDC currently recommends that Beyfortus is generally not needed for that infant, unless maternal antibody transfer was incomplete (e.g., premature birth, maternal immune compromise)
• If Abrysvo was not given during pregnancy, Beyfortus is recommended for the infant before or at the start of RSV season
• In some high-risk scenarios, your pediatrician may recommend Beyfortus even if the mother was vaccinated

Guidance in this area is evolving. The bottom line: make sure one of these options is in place for your newborn's first RSV season. Talk to both your OB (about Abrysvo) and your pediatrician (about Beyfortus) so there's no gap.

Safety during pregnancy

Abrysvo was evaluated in a large Phase 3 clinical trial in pregnant women. The FDA approved it based on data showing it was effective and had an acceptable safety profile. One finding in the trial was a modest increase in premature births in the vaccinated group, though subsequent analysis has not confirmed a causal relationship. The CDC and FDA consider the benefits to outweigh the risks for women in the approved window.

Discuss any concerns with your OB — particularly if you have a history of preterm labor. This is an evolving area and current CDC guidance may have been updated since this page was written.

What to tell your OB

At your appointment around 30–32 weeks, you can ask: "I'm interested in the RSV vaccine (Abrysvo) to protect my baby. Is my timing right for it and do you have it available?" Most OB practices that administer it will order it in advance. Don't assume it's automatic — ask explicitly.

Not medical advice. RSV vaccine recommendations during pregnancy are evolving. Always confirm current guidance with your OB, midwife, or healthcare provider.