British drugmaker GSK said on Friday the U.S. Food and Drug Administration has expanded the approved age range for its respiratory syncytial virus vaccine, Arexvy, to include adults aged 18 to 49 who are at increased risk of lower respiratory tract disease caused by the virus.

* Arexvy is already approved in the U.S. for preventing RSV-related disease in adults aged 60 and above, and in at-risk adults aged 50 to 59.

* RSV is a common respiratory virus that causes seasonal infections such as the flu and is a leading cause of pneumonia and death in infants and older adults.

* In the U.S., an estimated 21 million adults under 50 have at least one risk factor for severe RSV infection, the company said.

* GSK's vaccine, Arexvy, would be competing for market share in the 18-49 age group with Moderna's mRESVIA and Pfizer's Abrysvo.

* However, Arexvy first needs the U.S. Centers for Disease Control and Prevention's recommendation before it is made available for the age group.

* In December, a panel of the European Medicines Agency had also backed the use of Arexvy for all adults above the age of 18, paving the way for broader use.