Study Finds Pfizer’s RSV Vaccine Produces Strong Immune Response in Young Adults

Pfizer Inc.’s RSV vaccine produced immune responses in young adults at higher risk of severe illness just as well as in older people, leading the company to plan to apply for wider U.S. approval.

A single dose of the vaccine, called Abrysvo, generated a strong immune response in adults ages 18 to 59 with conditions such as asthma, diabetes, or chronic lung disease, Pfizer said. Based on the final-stage trial results, the company plans to ask the Food and Drug Administration to extend the shot’s approval to adults 18 and older.

RSV, or respiratory syncytial virus, is a flu-like illness that affects elderly adults and babies most severely. The market for adult vaccines alone could reach $11 billion by 2032, according to Bloomberg Intelligence, making it a lucrative target for drugmakers like Pfizer as sales of COVID-19 shots fade. Last year, Pfizer and GSK Plc were the first companies to reach the US market with RSV vaccines, and another made by Moderna is expected to gain U.S. approval next month.

Pfizer’s vaccine is now approved for adults 60 and up, as well as for use in pregnant women to protect newborns for up to six months after birth; sales were $890 million last year. Pfizer Chief Executive Officer Albert Bourla said in January that he was committed to stepping up efforts to take more market share for the vaccine in 2024.

No shots have yet been approved to prevent RSV in high-risk adults ages 18 and up, though Moderna is also running a trial in a similar population. Generally, these young adults don’t get as seriously ill from the virus as older people and babies do. The company is also conducting a study in immunocompromised patients 18 and older and expects to share results later this year.

Usage in younger adults would ultimately depend on the recommendation of the Centers for Disease Control and Prevention’s . If the vaccine were approved, the committee would have the flexibility to modify recommendations as appropriate, said Iona Munjal, executive director of clinical vaccines R&D at Pfizer.

GSK is exploring the possibility of running a clinical trial in patients younger than 50, but is currently focused on adult populations with the highest risk of RSV, according to a spokesperson. The company for FDA approval to extend RSV vaccination to adults 50 to 59 years old who are at increased risk of disease.

Pfizer’s trial included 681 people, roughly two-thirds of whom got one dose of the vaccine while one-third received a placebo.