FDA Approves Two RSV Vaccines for Older Adults, and an Advisory Panel Recommended Another to Protect Infants

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This fall and winter are likely to be a good bit safer for older people and soon for infants as vaccines and treatments against respiratory syncytial virus (RSV) move through the FDA’s approval process.

Early last month, the agency approved the first vaccine against RSV in the United States, for adults ages 60 and older, from GSK. It green-lit a second one, from Pfizer, yesterday.

In between those two approvals an FDA advisory panel unanimously recommended approval of a Pfizer RSV vaccine that would be given late in pregnancy to protect newborns.

And it’s not only vaccines that are making their way through the approval process and eventually into clinical practice. The FDA’s Antimicrobial Drugs Advisory Committee is scheduled to consider a monoclonal antibody treatment for RSV in infants on June 8. If the committee recommends approval of the AstraZeneca and Sanofi treatment, the FDA would likely make a final decision in September.

The monoclonal antibody treatment, administered as an injection, is intended to provide five months of protection. A similar treatment from Merck is in clinical trials.

Vaccines for older adults

Respiratory syncytial (pronounced sin-SISH-uhl) virus can be lethal for elderly people who are frail or live in institutions. Between 60,000 and 160,000 people ages 65 and older are hospitalized annually in the United States because of RSV illness and 6,000 to 10,000 die.

The GSK vaccine that the FDA approved for that age group on May 3 is expected to launch in the fall under the brand name Arexvy. In the main study to assess the safety and effectiveness of a single dose given to individuals 60 and older, about 12,500 participants received the vaccine and a similar number got a placebo.

The intervention group had an 83% reduced risk of developing RSV-associated lower respiratory tract disease and a 94% reduced risk of severe disease. Participants will remain in the study for two more RSV seasons to assess the safety and effectiveness of repeat shots.

“Approval of the first RSV vaccine is an important public health achievement to prevent a disease which can be life-threatening and reflects the FDA’s continued commitment to facilitating the development of safe and effective vaccines for use in the United States,” Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research, said in a press release.

This week’s approval of Pfizer’s vaccine for the same age group, to be sold as Abrysvo, was based on data from an international clinical trial with nearly 36,000 participants ages 60 and over that showed 67% efficacy against RSV-associated illness and 86% against disease with three or more signs or symptoms.

Results from the clinical trials of both vaccines identified possibe safety concerns that warrant further study: two cases of Guillain-Barré syndrome in the Pfizer trial (the main reason for a 7 to 4 vote in favor of safety and efficacy by the advisory panel that recommended it three months ago) and one case of Guillain-Barré plus two others of a possibly related disorder in the GSK trial (leading to a 10 to 2 vote recommending approval).

CDC’s Advisory Committee on Immunization Practices, which makes recommendations that are influential in how vaccines get used in clinical practice, is scheduled to discuss the vaccines on June 21.

Moderna also is developing an RSV vaccine for older adults and has said that it expects to file an application for FDA authorization in the first half of this year. Moderna’s vaccine is mRNA-based, which the company said allowed it to move from phase 1 to phase 3 clinical trials in less than 2-1/2 years, much faster than the industry average. The GSK and Pfizer vaccines are protein-based.

Vaccine for infants

RSV infections are very common in children, causing an estimated 2.1 million doctor visits a year in the U.S. due to runny nose, coughing, sneezing and low fever. Although it usually resolves without serious illness, severe infections put 58,000 to 80,000 children younger than 5 in the hospital each year and kills up to 300, the vast majority of whom are younger than 6-months-old. This past winter was unusually deadly, with a “tripledemic” of RSV, influenza and COVID-19 overwhelming children’s hospitals.

The Pfizer vaccine that was recommended for approval on May 18 by the FDA’s Vaccines and Related Biological Products Advisory Committee was tested in a clinical trial of about 7,300 women, half of whom received the vaccine after 24 weeks of pregnancy; the other half got a placebo shot. Efficacy of the prefusion F vaccine (RSVpreF) candidate was 82% against severe disease after 90 days and 69% after 180.

Although all 14 advisory committee members voted for approval, just 10 signed off on safety. Rates of preterm births were higher in the vaccine group, but the difference was not statistically significant. The FDA is expected to decide on approval in August.