Pfizer's RSV vaccine, Abrysvo, shows promising tolerance and immune response in high-risk adults aged 18 to 59, paralleling results in older adults.

Pfizer is aiming for FDA approval to use Abrysvo in a broader age group of adults, extending from 18 to 59 years old.

Competitor GSK is also pursuing an expanded age range for its RSV vaccine, Arexvy, and awaits FDA decision on 50 to 59 age group by June 7.

RSV is a significant cause of pneumonia among toddlers and the elderly, highlighting the importance of effective vaccines.

Pfizer's late-stage trial included 681 adults with conditions like asthma and diabetes, confirming a strong immune response akin to that in older adults.

Some experts remain skeptical about the substantial clinical benefit of RSV vaccines for most high-risk individuals.

Pfizer's push to expand the use of Abrysvo is part of its strategy to compete with GSK, which already has an FDA-approved RSV vaccine for adults.