FDA Approves Pfizer RSV Vaccine for Use During Pregnancy to Protect Infants

The FDA has approved Pfizer’s bivalent respiratory syncytial virus (RSV) vaccine (Abrysvo) for use during pregnancy to prevent lower respiratory tract disease (LRTD) and severe LRTD caused by RSV in infants from birth through 6 months, according to a press release.¹ The approval makes Abrysvo the first and only maternal RSV vaccine used to help protect infants from the virus.

RSV is a highly contagious virus that causes respiratory infections and can infect people of all ages, but it’s especially common in children. It is the leading cause of respiratory-related hospitalizations in infants worldwide and is the main cause of hospitalizations in the first year of life.² Although the virus often only causes cold-like symptoms, it also can lead to pneumonia and bronchiolitis.

“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,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said in a release. “This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.”

The approval of Abrysvo was based on efficacy data from the phase 3 clinical trial MATISSE (NCT04424316). The study included 3682 maternal participants who received the vaccine and 3676 who received a placebo at 24 through 36 weeks gestation, with 3570 and 3558 infants evaluated, respectively. Abrysvo reduced the risk of severe LRTD by 81.8% within 90 days after birth, and 69.4% within 180 days after birth.

The safety of Abrysvo was evaluated in two studies. The first study included 3,600 pregnant individuals who received a single dose and 3,600 pregnant individuals who received a placebo. In the second, 100 received Abrysvo and 100 received placebo. The most commonly reported side effects included injection site pain, headache, muscle pain and nausea. Additionally, pre-eclampsia was reported in 1.8% of participants.

“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,” Eric A.F. Simões, MD, said in a release.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.”

Abrysvo includes a boxed warning that a numerical imbalance in preterm births recipients occurred compared to those who received placebo. The available data currently are insufficient to establish or exclude a causal relationship. The FDA noted that it is requiring Pfizer to conduct postmarketing studies to assess the signal of serious risk of preterm birth and hypertensive disorders of pregnancy, including pre-eclampsia.

References

1. FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants. News Release. FDA. August 21, 2023. Accessed August 22, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-vaccine-pregnant-individuals-prevent-rsv-infants

2. Halasa N, Zambrano LD, Amarin JZ, et al. Infants Admitted to US Intensive Care Units for RSV Infection During the 2022 Seasonal Peak. JAMA Netw Open. 2023;6(8):e2328950. doi:10.1001/jamanetworkopen.2023.28950

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 22, 2023. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-abrysvotm-pfizers-vaccine-prevention-0