Phase 3 Evaluation of Safety and Immune Response to a Second Dose of Bivalent RSV Vaccine During Pregnancy and Duration of Protection from a Previous Dose

What this Trial Is About

Researchers are evaluating the safety and immune response of a second dose of the RSVpreF vaccine in pregnant women during later pregnancies. The study also aims to understand how long the protection lasts from a single dose given during a previous pregnancy by examining blood samples from nonpregnant participants who had the vaccine before. This Phase 3 trial involves pregnant participants and their unborn babies, as well as nonpregnant participants previously vaccinated. Pregnant participants are divided into two groups one group who previously received RSVpreF in a Pfizer trial will get a second dose, and another group will be randomly assigned to receive either RSVpreF or a placebo if no prior antibody data exists. Infants born to these participants will be followed for six months to monitor safety and antibody levels. Nonpregnant participants who received RSVpreF in an earlier trial will provide blood samples to assess the durability of their immune response without receiving additional vaccine doses. Participants will undergo safety monitoring including tracking local and systemic reactions, adverse events, and serious events during pregnancy and after birth for infants. Blood tests will measure neutralizing antibodies against RSV types A and B at birth, 3 months, and 6 months. The study includes consent procedures for both pregnant participants and infants, and nonpregnant participants will have scheduled visits for blood sample collection. The total study duration extends through infant follow-up and ongoing immune response assessments.

A Phase 3 Study of Revaccination in Subsequent Pregnancies With Bivalent RSV Vaccine and Duration of Protection of a Single Dose