The U.S. Food and Drug Administration (FDA) has approved Pfizer's Abrysvo vaccine for the prevention of lower respiratory tract disease (LRTD) caused by respiratory syncytial virus (RSV) in adults aged 18 to 59 years who are at increased risk. This expands the vaccine's availability to a younger population, offering the broadest RSV vaccine indication for adults.
Clinical Trial Data
The FDA's approval is based on data from the Phase 3 MONeT clinical trial (NCT05842967), a randomized, double-blind, placebo-controlled study involving 681 adults aged 18 to 59 years with chronic pulmonary, cardiovascular, renal, hepatic, neurologic, hematologic, or metabolic disorders. Participants were randomized 2:1 to receive a single dose of Abrysvo or placebo.
The MONeT trial demonstrated that Abrysvo met its co-primary immunogenicity endpoints, showing non-inferior neutralizing responses for RSV-A and RSV-B compared to responses observed in the Phase 3 RENOIR study of Abrysvo in adults 60 years of age and older. Furthermore, there was at least a 4-fold increase in neutralizing titers for RSV-A and RSV-B one month after vaccination compared to pre-vaccination levels.
Safety and Tolerability
In the MONeT trial, Abrysvo was generally well-tolerated. The most common adverse reactions reported in individuals 18 to 59 years of age were pain at the injection site, muscle pain, joint pain, and nausea. These findings are consistent with the safety profile observed in previous studies of Abrysvo in other populations.
Impact and Context
According to Pfizer, approximately 9.5% of adults aged 18 to 49 in the U.S. have an underlying chronic condition, such as obesity, diabetes, chronic obstructive pulmonary disease (COPD), heart failure, chronic kidney disease, or asthma, that puts them at increased risk of developing and being hospitalized for RSV-associated LRTD. This percentage rises to 24.3% among adults aged 50 to 64.
“RSV represents a significant threat to younger adults with certain chronic conditions,” said Aamir Malik, Chief U.S. Commercial Officer and Executive Vice President, Pfizer. “With this approval, we are proud that Abrysvo is now the only RSV vaccine indicated for adults aged 18 to 49 at increased risk for the disease, expanding on its existing indications for older adults and pregnant women.”
Abrysvo is also approved for adults 60 years and older and for pregnant individuals at 32 through 36 weeks of gestation to protect infants from birth up to 6 months of age. The vaccine is an unadjuvanted, bivalent RSV prefusion F (RSVpreF) vaccine designed to provide broad protection against RSV-LRTD, regardless of the virus subgroup.
