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The FDA has for preventing lower respiratory infections in adults 60 and over, Pfizer announced on Wednesday.

Approval of the unadjuvanted, bivalent RSV prefusion F protein vaccine (Abrysvo) follows an endorsement in March from FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC). Advisors voted 7-4 in support of the vaccine's efficacy and safety data, which were primarily derived from the .

The phase III study included roughly 37,000 participants, ages 60 and up, who were randomized to either a single intramuscular injection dose of vaccine (120 µg) or placebo. At an interim analysis, vaccine efficacy reached 66.7% against two or more lower respiratory tract RSV symptoms (96.66% CI 28.8-85.8) and 85.7% against three or more symptoms (96.66% CI 32.0-98.7), meeting the co-primary endpoints of the study.

"This past RSV season demonstrated the serious consequences and potential health risks this virus poses for older adults," said principal RENOIR investigator Edward Walsh, MD, of the University of Rochester Medical Center in New York, in a statement from the drugmaker.

"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," he added.

Safe and effective RSV vaccines have been elusive and decades in the making. Until the approval of GSK's adjuvanted RSV prefusion F protein-based vaccine (Arexvy) earlier this month, no vaccine had existed to protect against RSV infections, which can turn serious for young children and older adults. A previous attempt using a resulted in enhanced infections in children naive to the virus.

According to , an estimated 60,000 to 160,000 older adults in the U.S. are hospitalized each year due to RSV infections, and 6,000 to 10,000 deaths are associated with the highly contagious virus in this group. Risk factors for severe disease include increasing age, asthma, heart failure, and chronic obstructive pulmonary disease.

VRBPAC also recently weighed in on Pfizer's RSV prefusion F protein vaccine given to mothers in the third trimester for preventing infections in infants, with the committee voting 14-0 on efficacy and 10-4 on safety. The company said it plans to study the vaccine in multiple other age groups as well, including healthy children ages 2-5 years, and other high-risk groups.

Common adverse events (≥10%) with the product included pain at the injection site, fatigue, headache, and muscle pain; and includes contraindications for people with a history of severe allergic reactions to any components of the vaccine. Pfizer also noted that fainting can happen after vaccine administration, and that individuals with a weakened immune system may have a reduced response to the product.

The company said it expects the vaccine to be available for older adults in the fall, with the on June 21 to discuss recommendations for its appropriate use in older adults.

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