By Marie Rosenthal, MS
The FDA granted a new indication for Pfizer’s respiratory syncytial virus prefusion F (RSVpreF) vaccine (Abrysvo) to prevent lower respiratory tract disease (LRTD) in younger adults whose chronic condition could put them at risk for disease.
The vaccine is now indicated for people with certain chronic conditions who are 18 through 59 years of age. These conditions include cardiovascular disease, diabetes, obesity, asthma, chronic obstructive pulmonary disease, liver and kidney diseases, as well as people taking long-term steroids or immunomodulating medications. Among U.S. adults 18 to 49 years of age, 9.5% have an underlying chronic condition that puts them at increased risk of developing, and being hospitalized for, RSV-associated LRTD, and this rises to 24.3% among those 50 to 64 years of age, according to Pfizer.
The FDA’s decision is based on inferred efficacy from the pivotal phase 3 clinical trial (ClinicalTrials.gov Identifier: NCT05842967) MONeT (RSV IMmunizatiON Study for AdulTs at Higher Risk of Severe Illness), which investigated the safety, tolerability and immunogenicity of RSVpreF in adults at risk for RSV due to certain chronic medical conditions.
Substudy B of the MONeT trial was conducted to assess the safety and immunogenicity of two doses of RSVpreF, administered one month apart, in four groups of immunocompromised adults: those with non-small cell lung cancer, those on hemodialysis due to end-stage renal disease, those with autoimmune inflammatory disorder receiving active immunomodulator therapy and solid-organ transplant recipients. Of the 203 adults enrolled in the substudy, approximately half were between the ages of 18 and 59, and approximately half were 60 years and older, according to data released in August.
The RSVpreF vaccine was well tolerated during the trial, showing a safety profile consistent with findings from other studies of the vaccine. While the company evaluated two doses, a single dose generated a strong neutralizing response against both subtypes of RSV, RSV-A and RSV-B, across all cohorts and age groups studied.
This RSV vaccine is the only one indicated to help protect adults 60 and older, and adults 18 and older at increased risk for RSV-LRTD, as well as infants through maternal immunization. The RSVpreF vaccine is an unadjuvanted, bivalent vaccine that was designed to provide broad protection against RSV-LRTD, regardless of the virus subgroup. In the prefusion state, the RSV fusion protein (F) is a major target of neutralizing antibodies, serving as the basis of Pfizer’s RSV vaccine. Variations in the F protein sequence among RSV-A and RSV-B subgroups are clustered in a key antigenic site, a target for potent neutralizing antibodies.
In May 2023, the FDA approved RSVpreF vaccine for the prevention of LRTD caused by RSV in individuals 60 years of age and older. In June 2024, the Advisory Committee on Immunization Practices (ACIP) voted to update its recommendation of RSV vaccines for use in adults at least 75 years and those between 60 and 74 years who are increased risk for severe RSV disease. In August 2023, the FDA approved the RSVpreF vaccine for the prevention of LRTD and severe LRTD caused by RSV in infants from birth up to 6 months of age by active immunization of pregnant individuals at 32 through 36 weeks’ gestational age. This was followed in September 2023 with ACIP’s recommendation for maternal immunization to help protect newborns from RSV seasonally where the vaccine should be administered from September through January in most of the continental United States.
“RSV represents a significant threat to younger adults with certain chronic conditions. After decades of vaccine research by the scientific community and Pfizer, we now have the opportunity to help alleviate the burden of RSV in this high-risk adult population,” said Aamir Malik, Pfizer’s chief U.S. Commercial Officer and executive vice president.
The company intends to submit results from MONeT for publication in a peer-reviewed scientific journal and for presentation at an upcoming scientific conference.
