Pfizer revealed on Wednesday that the FDA has granted approval for a second respiratory syncytial virus (RSV) vaccine, specifically designed to prevent lower respiratory infections in adults aged 60 and over.
This approval for the unadjuvanted, bivalent RSV prefusion F protein vaccine, known as Abrysvo, comes after an endorsement from the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) in March. The committee voted 7-4 in favor of the vaccine’s efficacy and safety data, which were primarily derived from the RENOIR trial.
The phase III study involved approximately 37,000 participants aged 60 and above, who were randomly assigned to receive a single intramuscular injection dose of the vaccine (120 µg) or a placebo. The interim analysis demonstrated that the vaccine achieved 66.7% efficacy against two or lower respiratory tract RSV symptoms (with a 96.66% confidence interval of 28.8-85.8) and 85.7% efficacy against three or more symptoms (with a 96.66% confidence interval of 32.0-98.7), successfully meeting the co-primary endpoints of the study.
Edward Walsh, MD, the principal investigator of RENOIR at the University of Rochester Medical Center in New York, emphasized the importance of this approval: “This past RSV season demonstrated the serious consequences and potential health risks this virus poses for older adults. Today’s FDA approval of Abrysvo recognizes significant scientific progress and importantly helps provide older adults potential protection against RSV and an opportunity to improve community health by helping prevent the disease.”
Developing safe and effective RSV vaccines has been a challenging and lengthy process. Prior to the recent approval of GSK’s adjuvanted RSV prefusion F protein-based vaccine (Arexvy), no vaccines existed to safeguard against RSV infections, which can have severe consequences for young children and older adults. Previous attempts using a formalin-inactivated RSV vaccine in the late 1960s resulted in enhanced infections in children lacking prior exposure to the virus.
According to CDC data, an estimated 60,000 to 160,000 older adults in the U.S. are hospitalized annually due to RSV infections, with 6,000 to 10,000 deaths associated with this highly contagious virus in this age group. Risk factors for severe disease include advancing age, asthma, heart failure, and chronic obstructive pulmonary disease.
VRBPAC also recently assessed Pfizer’s RSV prefusion F protein vaccine administered to mothers in the third trimester to prevent infections in infants. The committee voted 14-0 on efficacy and 10-4 on safety. Pfizer intends to conduct further studies on the vaccine in multiple age groups, including healthy children aged 2-5 years and other high-risk populations.
Common adverse events (≥10%) observed with the vaccine included pain at the injection site, fatigue, headache, and muscle pain. The vaccine’s labeling contains contraindications for individuals with a history of severe allergic reactions to any components of the vaccine. Pfizer also cautioned that fainting may occur after vaccine administration, and individuals with weakened immune systems may have a reduced response to the product.
The company anticipates that the vaccine will be available for older adults in the fall, with the CDC’s Advisory Committee on Immunization Practices convening on June 21 to discuss recommendations regarding its appropriate use in this age group.