Pfizer to Ask for Approval for RSV Vaccine for People as Young as 18


Pfizer on April 9 said it will ask U.S. regulators to approve its respiratory syncytial virus (RSV) vaccine for people as young as 18.

The pharmaceutical company said that data from an ongoing phase 3 trial showed the vaccine generated an immune response in people deemed at risk of developing severe illness associated with RSV, similar to the immune response generated in adults aged 65 and up. The vaccine is already approved in the United States for the latter group.

Based on the results, Pfizer will ask the U.S. Food and Drug Administration (FDA) for expanded approval for the vaccine.

“This represents a real opportunity for an expansion to an age population in a risk population that wouldn’t normally see the availability of this vaccine so soon,” said Dr. Iona Munjal, executive director of clinical vaccine research and development at Pfizer.

The company did not give a time frame for when it expects the data to be considered by regulators, and the FDA has said it does not comment on pending submissions.

Pfizer launched Abrysvo, the vaccine, for older adults and pregnant women in 2023. GSK also launched its rival vaccine Arexvy that year.

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GSK, based in the United Kingdom, is also looking to expand the age range for its shot and has already submitted data for adults ages 50 to 59 to U.S. regulators. The FDA is expected to decide on whether to approve the label expansion by June 7, which could allow GSK to offer its shot in the younger age group later this year.

Pfizer did not say whether it expects to be able to expand Abrysvo’s label in time for the 2024-25 respiratory virus season, which starts near the end of the year.

RSV, which typically causes cold-like symptoms, is a leading cause of pneumonia in toddlers and older adults.

Uptake of RSV vaccines has been slow in the United States. Just 23.6 percent of seniors reported receiving a shot, according to survey data from the U.S. Centers for Disease Control and Prevention.

In the phase 3 Pfizer trial involving 681 adults aged 18 to 59 with conditions including asthma, diabetes, and chronic obstructive pulmonary disease that increase the risk from RSV, the company relied on a technique called immunobridging, which bypasses clinical efficacy estimates and instead compares the immune response in the tested group to that in a population for which the drug or vaccine is already approved.

“The use of immunobridging studies to extrapolate efficacy from older to younger adults is an established regulatory pathway,” Pfizer said in a statement.

Critics say trials should present efficacy data.

In the tested group, the immune response after a shot was non-inferior to the one observed in older adults, according to Pfizer. Neutralizing titers in blood for RSV also jumped at least four times as high following receipt of a shot, compared to levels before vaccination, according to the company.

The company did not provide many details on the safety results from the trial. It said the shot was “well-tolerated” and that the safety data were “consistent with those from previous investigations.”

Pfizer plans to have the results published in a peer-reviewed journal.

The company said those with a higher risk profile represent 9.5 percent of U.S. adults 18 to 49 years of age and nearly a quarter of those between the ages of 50 and 64.

Dr. David Boulware, an infectious disease specialist at the University of Minnesota, said he was not sure most Americans who fit those high-risk categories would need the shot.

“The clinical benefit is likely going to be relatively low for most people,” he said.

People who have had organ transplants, are undergoing chemotherapy for cancer, or are survivors of congenital disease would clinically benefit from the shot, he suggested.

Reuters contributed to this report.


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