Pregnancy vaccine or newborn antibody? For RSV, both held up

Expectant parents now have two ways to shield a newborn from RSV. The mother can get a vaccine during pregnancy, called RSVpreF, or the baby can get nirsevimab, a long-acting antibody given after birth. Which works better?

Researchers at Kaiser Permanente Northern California looked at full-term babies born across the 2023–24 and 2024–25 RSV seasons. Their main comparison matched 11,293 infants whose mothers were vaccinated with 3,831 who received the antibody.

Compared with babies who had neither, maternal vaccination was associated with 69.3% effectiveness against infection and 86.4% against hospitalization. For nirsevimab, the figures were 65.2% and 73.8%.

Head to head, the study found no statistically significant difference. That doesn't prove the two are identical. Just 12 babies were hospitalized in the main comparison, too few to rule out smaller differences.

This was a look back at health records, not a trial. Families who chose each option may differ in ways the data didn't capture, and testing was at clinicians' discretion. The results cover full-term infants in one insured California system. Some authors reported outside grants from vaccine makers, including Pfizer, Moderna, Sanofi, and GSK.