FDA Approves First RSV Vaccine for Use in Pregnant Individuals to Prevent LRTD in Infants

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The US Food and Drug Administration (FDA) 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.

The agency approved Abrysvo™ (Pfizer) for use as a single intramuscular injection at 32 through 36 weeks’ gestational age, according to the August 21, 2022, press release.¹

“RSV is a common cause of illness in children, and infants are among those at highest risk for severe disease, which can lead to hospitalization,” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, in the release. “This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.”¹

The approval came 3 months after the FDA approved Abrysvo for the prevention of LRTD caused by RSV in persons aged ≥60 years, an age group at risk for serious illness.

RSV is particularly common in children, with most individuals expected to be infected with RSV by 2 years of age, said the FDA. RSV often causes cold-like symptoms in infants and young children, as well as LRTD, such as pneumonia and bronchiolitis, added the agency.¹

“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 Simões, MD, clinical professor, pediatrics-infectious diseases, University of Colorado School of Medicine, Children’s Hospital Colorado, Aurora, in a Pfizer press release.² “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.”

The FDA decision was based on data from the global phase 3 clinical trial MATISSE (MATernal Immunization Study for Safety and Efficacy) that investigated the efficacy of Abrysvo to protect infants after birth when the shot is given to pregnant individuals.² Approximately 7400 pregnant individuals aged ≤49 years were randomized in a 1:1 ratio to receive a single dose of either Abrysvo 120 µg or placebo during the late second to third trimester of their pregnancy.

Pfizer announced the results in November 2022, which showed that at 90 days after birth, the vaccine’s efficacy was 57.1% against RSV-positive, medically attended lower respiratory tract illness (MA-LRTI) and 81.8% against RSV-positive severe MA-LRTI in infants.²

According to the FDA, the most commonly reported side effects by pregnant individuals who received Abrysvo were pain at the injection site, headache, muscle pain, and nausea in 2 clinical trials that analyzed the safety of the RSV vaccine.¹

“In addition, although not commonly reported…pre-eclampsia occurred in 1.8% of pregnant individuals who received Abrysvo compared to 1.4% of pregnant individuals who received placebo,” the release said. “In the safety studies, low birth weight and jaundice in infants occurred at a higher rate in the pregnant Abrysvo recipients compared to pregnant placebo recipients.”¹

In addition, one adverse event noted in the safety studies that is included as a warning in the prescribing information was preterm birth, which was reported by 5.7% of pregnant individuals who received Abrysvo and 4.7% of pregnant individuals in the placebo group.1 However, the FDA noted, that the available data are “insufficient to establish or exclude a causal relationship between preterm birth and Abrysvo.”¹

“Specifically, the warning informs healthcare providers that to avoid the potential risk of preterm birth with use of Abrysvo before 32 weeks of gestation, administer Abrysvo as indicated in pregnant individuals at 32 through 36 weeks gestational age,” continued the agency.¹

According to the agency’s statement, the FDA is requiring Pfizer to conduct postmarketing studies to examine the signal of serious risk of preterm birth and to assess hypertensive disorders in pregnant women, including pre-eclampsia.¹

References:

1. FDA approves first vaccine for pregnant individuals to prevent RSV in infants. FDA, Press release. August 21, 2023. Accessed August 22, 2022. https://www.fda.gov/news-events/press-announcements/fda-approves-first-vaccine-pregnant-individuals-prevent-rsv-infants
2. US 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. Pfizer. Press release. August 21, 2023. Accessed August 22, 2023. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-abrysvotm-pfizers-vaccine-prevention-0