FDA AdComm backs Pfizer maternal RSV vax

May 19, 2023

Earlier this week, an FDA Advisory Committee voted to back Pfizer’s RSV vaccine candidate, Abrysvo, for infants younger than 6 months when administered during the second or third trimester of pregnancy in maternal patients. 

During the Vaccines and Related Biological Products Advisory Committee meeting, advisors combed through Pfizer’s findings and discussed the jab’s efficacy and safety profiles. The data included results from its Matisse maternal vaccine study, which supported the drug’s Biologics License Application. 

Out of the maternal participants, the cohorts were divided so that 3570 infants received the and 3558 infants received placebo. The study found that within 90 days of birth, the vaccine had 81.8% efficacy, and 69.4% after 6 months. Following discussions, members unanimously voted 14-0 on behalf of the jab's efficacy data, but had more divided conclusions regarding its safety data, with 10 voting in favor and four opposed.

Advisors' hesitancy revolved around infant safety data. A few committee members pointed out an incident in which an infant was born at 36 weeks and 5 days and delivered 86 days after the mother received the vaccine. While the baby had a normal birth without complications, the event was found to be correlated to the vaccine. 

Abrysvo is designed to promote the synthesis of maternal serum anti-F immunoglobulin G and transfer across the placenta to the fetus, providing protection to the infant during the first six months of life when there is a heightened vulnerability to hospitalization as a result from infection.

The vaccine’s BLA was granted priority review, and its regulatory action date is scheduled for August 21, 2023. 

It's been a heated race in the RSV space. Earlier this month, GSK grabbed the first FDA approval its RSV jab — to be sold as Arexvy — for preventing lower respiratory tract disease in individuals 60 years of age and older. The approval marks the first-ever RSV vaccine for older adults to be approved globally.