FDA Approves RSV Vaccine for Pregnant Individuals to Prevent Virus in Infants

The FDA has approved the first vaccine for use in pregnant individuals to prevent lower respiratory tract disease (LRTD) and severe LRTD caused by respiratory syncytial virus (RSV) in infants from birth through 6 months of age.¹

This is the second indication for Pfizer's bivalent RSV prefusion F (RSVpreF) vaccine. In May 2023, the vaccine was approved for the prevention of LRTD caused by RSV in individuals 60 years and older.²

Abrysvo is the first maternal vaccine to protect infants up to 6 months of age from respiratory syncytial virus.

The approval for the new indication was based on a pivotal trial in more than 7000 pregnant individuals. Participants were immunized between 32 and 36 weeks of gestational age.

“Abrysvo’s approval as the first and only maternal immunization to help protect newborns immediately at birth through six months from RSV marks a significant milestone for the scientific community and for public health,” Annaliesa Anderson, PhD, senior vice president and chief scientific officer, Vaccine Research and Development, Pfizer, said in a statement.³ "Today, a long-sought-after goal to deliver a maternal vaccine that will help protect infants six months of age or younger—when they are at greatest risk of possible serious consequences from RSV—has been achieved.”

The phase 3 clinical trial (NCT04424316) MATISSE (MATernal Immunization Study for Safety and Efficacy), was a randomized, double-blinded, placebo-controlled study designed to evaluate the efficacy, safety, and immunogenicity of the vaccine. The results were published in New England Journal of Medicine.⁴

In the trial, 3682 maternal participants received the vaccine and 3676 received placebo. Subsequently, 3570 babies of individuals who received the vaccine and 3558 babies of those who received placebo were evaluated.

Within 90 days of birth, 6 infants of individuals who received the vaccine and 33 infants of individuals in the placebo group developed severe LRTD. The most common adverse events (≥10%) in pregnant individuals were pain at the injection site, headache, muscle pain, and nausea. RSV-associated lower respiratory tract illness occurred within 90 days after birth in 24 infants in the vaccine group and 56 infants in the placebo group.

Within 1 month after birth, 37.1% of infants in the vaccine group and 34.5% in the placebo group had developed any adverse events. Among the maternal participants, incidences of serious adverse events through 6 months after injection and incidences of premature delivery were similar in the 2 groups.

Individuals with high-risk pregnancies were excluded from the trial, and the researchers noted that infants born to these individuals could be at higher risk for severe RSV-associated illness.

“Newborns and young infants—whose immune systems are still developing and are not yet strong enough to defend against infections—may now be protected from RSV from the moment of birth through maternal immunization,” said Eric A.F. Simões, MD, clinical professor, Pediatrics-Infectious Diseases, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora.³ “The approval of Pfizer’s ABRYSVO is a major triumph as it helps ensure no delay in potential RSV protection during an infant’s most vulnerable first six months of life and offers healthcare providers a new opportunity to help prevent severe RSV.”

Pfizer has initiated 2 additional clinical trials evaluating Abrysvo: (1) in children aged 2 to 18 years who are at higher risk for RSV disease and (2) in adults aged 18 to 60 years who are at higher risk for RSV due to underlying medical conditions, such as asthma, diabetes, and chronic obstructive pulmonary diseaes, and adults 18 years and older who are immunocompromised and at high risk for RSV.

References

1. FDA approves first vaccine for pregnant individuals to prevent RSV in infants. News release. FDA. August 21, 2023. Accessed August 21, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-vaccine-pregnant-individuals-prevent-rsv-infants

2. U.S. FDA approves Abrysvo, Pfizer’s vaccine for the prevention of respiratory syncytial virus (RSV) in older adults. News release. Pfizer. May 31, 2023.Accessed August 21, 2023. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-abrysvotm-pfizers-vaccine-prevention

3. U.S. FDA approves Abrysvo, Pfizer’s vaccine for the prevention of respiratory syncytial virus (RSV) in infants through active immunization of pregnant individuals 32-36 weeks of gestational age. News release. Pfizer. August 21, 2023. Accessed August 21, 2023. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-abrysvotm-pfizers-vaccine-prevention-0

4. Kampmann B, Madhi SA, Munjal I, et al; MATISSE Study Group.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants. N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480