Pfizer presents data to CDC on maternal RSV vaccine up for FDA review

Pfizer presented data for the first time publicly Thursday on its maternal vaccine candidate for respiratory syncytial virus, which was granted priority review this week by the FDA.

The vaccine, RSVpreF, was previously granted priority review for older adults.

There are currently no vaccines or therapies for RSV, which hospitalizes up to 80,000 children and 160,000 older adults each year, according to the CDC.

The FDA said it will decide by August whether to approve the vaccine for pregnant people. It is expected to make a decision on the previous application for older adults in May.

“If approved, RSVpreF would help protect infants at their first breath from the devastating effects of this infectious disease, which though well known, [have] been particularly evident throughout this RSV season,” Annaliesa Anderson, PhD, senior vice president and chief scientific officer of vaccine research and development at Pfizer, said in a press release.

The company’s filings were supported by results from a phase 3 clinical trial evaluating the efficacy, safety and immunogenicity of RSVpreF against medically attended lower respiratory tract illness, or MA-LRTI, and severe MA-LRTI in infants born to healthy women vaccinated during pregnancy.

In a presentation to the CDC’s Advisory Committee on Immunization Practices, Iona Munjal, MD senior director of vaccine research and development at Pfizer, said the total dose level would be 120 g without an adjuvant, which equates to 60 g of each prefusion protein antigen in a 0.5 mL injection.

Munjal presented findings from the vphase 3 trial, including data showing that at 90 days after birth, vaccine efficacy was 57.1% (99.5% CI, 14.7%-79.8%) for RSV-positive MA-LRTI and 81.8% (99.5% CI, 40.6%-96.3%) for RSV-positive severe MA-LRTI. Neutralizing titers were also “robust” at 1 month after vaccination and remained so at delivery and postpartum, according to Munjal.

“The phase 3 trial demonstrated that the vaccine was well tolerated with a favorable benefit risk profile,” Munjal said.

Last year, an RSV surge hit children across the country, stretching hospital capacity. The disease, which usually operates in 2-year waves, was scarcely reported between 2020 and 2021, but in 2022 caused a substantial number of infections in the U.S. earlier in the season than what is typically seen and in numbers more typical of a pre-pandemic winter surge. The CDC also suggested in November that the surge could have occurred due to waning immunity among children.

As reported last year, AstraZeneca and Sanofi are currently developing nirsevimab, an investigational single-dose monoclonal antibody that has previously been shown to protect preterm infants against RSV.