Pfizer’s RSV Vaccine Wins Support From FDA Advisory Panel for Use in Older Adults

An advisory panel of the U.S. Food and Drug Administration (FDA) vaccine advisory group recommended approval of Pfizer’s ABRYSVO (RSVpreF), a bivalent vaccine indicated for the prevention of acute respiratory disease and lower respiratory tract disease caused by the human respiratory syncytial virus (RSV), for its use in people 60 and older on a 7-4 vote. 

If the FDA accepts the recommendations later on, the vaccine would probably become the first of its kind to be approved in the U.S. for protection from the notable respiratory pathogen.

Related article: Pfizer’s Bivalent RSV Candidate Demonstrates 85% Efficacy in Phase 3 Trials 

Older Adults Are at High Risk of RSV Infection

Human RSV is one of the most common viruses to infect children worldwide and nearly all children will experience at least one RSV infection by their second birthday. As adults, however, the virus is also increasingly recognized as an important pathogen and it may reinfect them over the course of their lives. 

Apart from infants and immunocompromised individuals, older adults are also at high risk for RSV infection and they are more prone to develop life-threatening symptoms. Currently, there are no specific treatment options for RSV infections. 

Heated Competition for the First FDA-approval

While none of the existing candidates has been approved by the FDA for the time being, RSV vaccine development, which has already been underway for nearly six decades, has made substantial progress in the past 10 years. It is estimated that the global RSV vaccine and antibody market will be worth US$2.56 billion in 2024 and rise to US$9.53 billion in 2028, with a compound annual growth rate of 38.90%. Major pharmaceutical companies such as Pfizer, GlaxoSmithKline (GSK), Moderna, Sanofi, Johnson & Johnson, and AstraZeneca have spent millions of dollars developing effective vaccines for RSV prevention and are racing to be the first to gain FDA approval in an attempt to capture the biggest share of this multi-billion dollar market. 

Among the many competitors in this space, 7 companies are conducting Phase 3 trials and some of these companies have already made significant regulatory breakthroughs. For example, in November 2022, AstraZeneca and Sanofi’s Beyfortus was granted approval in the European Union for its use in newborns and infants, while GSK announced an FDA acceptance for their older adult vaccine candidate for priority review in the same month. Furthermore, Pfizer announced last August that its bivalent candidate ABRYSVO (RSVpreF) demonstrated 85% efficacy in older adults in the Phase 3 RENOIR trials. 

A 7-4 Vote for Recommendation Despite Doubts

During the online meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) held on February 28 and March 1, the panel of experts discussed and made recommendations on the safety and effectiveness of Pfizer’s ABRYSVO and GSK’s AREXVY for their use in RSV prevention in adults 60 years of age and older. 

Regarding the discussion on Pfizer’s vaccine, the panel examined findings from six clinical trials that involved more than 34,000 participants. Overall, experts were positive about the efficacy findings, with 66.7% of lab-confirmed RSV cases with at least two symptoms prevented, and the figure was even higher for confirmed RSV cases with three symptoms. However, they also raised concerns about some data gaps, including the lack of data on hospitalizations and the highest-risk individuals (adults 60 years of age and older and those with underlying conditions). The vote passed with 7 voting yes, 4 no, and 1 abstention.

Concerning safety, experts found no major differences between the vaccinated and placebo groups in adverse events overall. Nevertheless, some of them were largely worried about its potential association with Guillain-Barré syndrome (GBS), a rare neurological disorder that damages nerve cells and causes muscle weakness or paralysis, as two cases were found in the vaccine group. The vote for this part also passed in the same distribution as the efficacy part. 

Paving the Way to the First FDA-approved RSV Vaccine

The FDA has already asked Pfizer to propose a postmarketing safety study to look closely at the risk of GBS among vaccine recipients. After gaining experts’ recommendations, the next step is for the FDA to approve the vaccine, which could take several months, even though the FDA usually follows advisory committee recommendations. Before the vaccine becomes available to the public, it must be recommended by the CDC after FDA approval. In the event that all of that occurs, ABRYSVO would be the first RSV vaccine to be approved in the U.S.

Author

Richard Chau