March 13 (Reuters) - 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.

* The vaccine 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 ( MRNA ) mRESVIA and

Pfizer's ( PFE ) Abrysvo.

* 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.

(Reporting by Siddhi Mahatole in Bengaluru; Editing by Devika

Syamnath)