FDA Approves Abrysvo to Prevent RSV in Infants

The FDA has approved Pfizer’s Abrysvo vaccine to prevent respiratory syncytial virus infections in infants through the age of six months. It is the first vaccine approved to be given to pregnant women at 32 to 36 weeks to prevent infection in infants. Abrysvo is administered as a single dose injection into the muscle.

RSV is a contagious virus and a common cause of respiratory illness. The virus can affect the lungs and breathing passages of an infected people and can potentially cause severe illness in young infants, older adults, and those with certain chronic medical conditions. Among children younger than five years old in the United States, RSV infections account for about 2.1 million outpatient visits and 58,000 hospitalizations each year.

Pfizer’s RSVpreF is a bivalent vaccine candidate that is composed of equal amounts of recombinant RSV prefusion F from subgroups A and B. The FDA approved Abrysvo in May for the prevention of RSV in people 60 years of age and older.

Eric A.F. Simões, M.D.

“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, M.D., clinical professor, Pediatrics-Infectious Diseases, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora, said in a press release.

The FDA’s decision is based on the data from the pivotal phase 3 clinical trial MATISSE, a placebo-controlled study designed to evaluate the efficacy, safety, and immunogenicity of the vaccine against lower respiratory tract disease due to RSV in infants born to healthy individuals vaccinated during pregnancy. These results were published in The New England Journal of Medicine in April 2023.

Abrysvo reduced the risk of severe lower respiratory tract disease by 81.8% within 90 days after birth, and 69.4% within 180 days after birth. In a subgroup of pregnant individuals who were 32 through 36 weeks gestational age, Abrysvo reduced the risk of lower respiratory tract disease by 34.7%, and reduced the risk of severe lower respiratory tract disease by 91.1% within 90 days after birth. Within 180 days after birth, Abrysvo reduced the risk of lower respiratory tract disease by 57.3%.

The most commonly reported side effects by pregnant individuals who received Abrysvo were pain at the injection site, headache, muscle pain and nausea. The prescribing information of Abrysvo warns about the risk of preterm birth, but FDA officials said there wasn’t enough data to establish a causal link to the vaccine. The agency is requiring Pfizer to conduct postmarketing studies to assess the risk of preterm birth, as well as the risk of pre-eclampsia.

In addition, Pfizer is investigating Abrysvo in other patient populations, including in children at higher risk for RSV disease ages 2 to less than 18, as well as in adults ages 18 to 60 at higher risk for RSV due to underlying medical conditions, such as asthma, diabetes and COPD.