Pfizer Wins FDA Approval for Vaccine against RSV in Older Adults

The US Food and Drug Administration (FDA) on Wednesday approved the Pfizer vaccine against respiratory syncytial virus (RSV) in older adults to be marketed as Abrysvo™. The bivalent RSV prefusion (RSVpreF) vaccine is indicated for prevention of lower respiratory tract disease (LRTD) caused by RSV in individuals aged ≥60 years.

The approval is the second milestone reached after more than 50 years of research to create the antigen that would safely elicit the most robust immune response to the virus. The Pfizer approval follows the FDA’s decision last month to greenlight Arexvy (RSVPreF3 +AS01E), the GSK vaccine to prevent LRTD caused by RSV, also in individuals aged ≥60 years.

“A vaccine to help prevent RSV had been an elusive public health goal for more than half a century," stated Annaliesa Anderson, PhD, Pfizer senior vice president and chief scientific officer of vaccine research and development in a company statement. “Abrysvo will address a need to help protect older adults against the potentially serious consequences of RSV disease.”

The FDA's decision was based on review of data from the pivotal Phase 3 clinical trial known as RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease). The global, randomized, double-blind, placebo-controlled study was designed to evaluate the efficacy, immunogenicity, and safety of a single dose of the vaccine in adults aged ≥60 years.

Approximately 37000 participants were enrolled in RENOIR, with half receiving RSVpreF 120 μg and the other half receiving placebo in a 1:1 ratio. In the study findings, originally reported in August 2022 and subsequently published in the New England Journal of Medicine, RSVpreF demonstrated 85.7% efficacy in older patients with severe RSV-associated LRTD, defined by ≥3 symptoms. The vaccine was well tolerated, and Pfizer did not report safety concerns.

RENOIR is an ongoing study, with efficacy data being collected during the second RSV season.

Edward E. Walsh, MD, Professor of Medicine at the University of Rochester Medical Center and principal investigator of the RENOIR trial, commented, "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.”

The US Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) is scheduled to meet on June 21, 2023, to discuss recommendations for appropriate use of both the Pfizer and GSK vaccines for older adults. Pfizer expects Abrysvo to be available in the third quarter of 2023, just ahead of the anticipated RSV season this fall, pending results from the ACIP meeting.

Early in May, Pfizer reported positive top-line results from a Phase 3 study that evaluated the safety and immunogenicity of RSVpreF coadministered with seasonal inactivated influenza vaccine in adults aged ≥65 years.

The company also plans to conduct multiple clinical trials evaluating RSVpreF in healthy children aged 2-5 years, children aged 5-18 years with comorbidities, adults aged 18-60 years with comorbidities, and adults aged ≥18 years who are immunocompromised and at high risk for adverse RSV outcomes.

In addition, Pfizer is seeking approval to administer RSVpreF to pregnant persons, with the goal of preventing medically attended LRTD (MA-LRTD) and severe MA-LRTD caused by RSV in infants from birth to 6 months of age.

The maternal vaccine was recently recommended for approval by the FDA’s Vaccines and Related Biological Products Advisory Committee and a decision is expected by August 21, 2023.