Pfizer Is Seeking FDA Approval For RSV Vaccine For Young Adults

Pfizer is planning on using data from a clinical trial it concluded last month to ask regulators to expand approval of its respiratory syncytial virus (RSV) vaccine, Abrysvo.

In a press release Tuesday, the big pharma giant said the vaccine was for all adults aged 18 and over.

Pfizer also said that it has begun a trial evaluating the drug in children ages 2-18 who are at higher risk for RSV disease.

The Defender reports: Family medicine physician Dr. Kat Lindley told The Defender she is concerned about the rush to promote vaccines to treat RSV when the vaccines have serious risks and there are other methods of prevention and treatment.

“In my almost 20 years of practice, I have found RSV to be an illness most common in babies 12 months and younger, very responsive to supportive treatment. In recent years we are seeing it in elderly and immunocompromised patients,” she said. “Again the key thing for all these age groups is early supportive therapy and monitoring as needed.”

Typically, she said, the 18-59 age group is not at risk for RSV.

Among a series of approvals for drugs and vaccines to treat RSV last year, the U.S. Food and Drug Administration (FDA) approved Pfizer’s Abrysvo for people age 60 or older in late May 2023.

In August 2023, the agency expanded Abrysvo’s approval to protect babies through the first six months of life by vaccinating pregnant mothers between 32-36 weeks of pregnancy, despite safety concerns.

The company reported positive results from its Phase 3 MONeT clinical trial in adults ages 18-59 at increased risk of developing severe RSV-associated lower respiratory tract disease.

If the drug is approved, Pfizer will be the first company to win approval for an RSV vaccine in that age group, which typically is not at risk for severe RSV.

The MONet trial examined Abrysvo among about 900 adults of varying ages in two subgroups — one group had chronic medical conditions and the other group was made up of immunocompromised people.

The company reported that one month after vaccination, trial participants showed a four-fold increase in neutralizing antibodies and that the drug was well-tolerated and “safety findings were consistent with those from previous investigations of ABRYSVO in other populations.”

The company reported that a single dose of the vaccine administered to adults in the trial demonstrated an immune response that was not worse than the response in adults over 60 in a similar trial.

Based on those results, the company said, it is using “immunobridging” to extrapolate the drug’s efficacy in younger adults.

Immunobridging is a method of inferring vaccine effectiveness for one group by comparing immune response markers, like the production of antibodies, to the immune response markers in another group for which efficacy is known.

If approved, the company could skip double-blind placebo-controlled efficacy trials for that population.

The results have not yet been peer-reviewed or published. Pfizer said it plans to submit the data to regulatory agencies and ask them to expand the drug indication. It also plans to publish the trial results.

Since launching Abrysvo last year, Pfizer has been trying to close the sales gap with vaccine rival GSK, whose Arexvy RSV vaccine for people ages 60 and older was approved first, in early May 2023.

Pfizer CEO Albert Bourla said that Abrysvo had been a “bad launch” for Pfizer and the company would be looking to boost its market share, FiercePharma reported.

The drug generated $890 million for Pfizer in 2023. GSK made roughly $1.5 billion for Arexvy.

The RSV vaccine market is estimated to be worth up to $10 billion by 2030.

During clinical trials for both the GSK and Pfizer vaccines among older adults, several participants were diagnosed with rare conditions such as Guillain-Barré syndrome and acute disseminated encephalomyelitis (ADEM). One of the trial participants who developed ADEM later died, according to the FDA.