LONDON, Nov 30 (Reuters) - GSK CEO Emma Walmsley said on Thursday that the British drugmaker's respiratory syncytial virus (RSV) vaccine was now expected to generate more than 1 billion pounds ($1.26 billion) in its first year on the market.

The shot, branded as Arexvy "will be more than a billion pounds in its first year, (it) has lots of headroom for growth," Walmsley said, speaking in a Reuters Newsmaker interview on Thursday.

GSK previously said full-year 2023 sales for the vaccine would likely be between 900 million pounds and 1 billion pounds following a strong U.S. launch. RSV is a leading cause of pneumonia in toddlers and the elderly.

"We’re delighted with the start of our RSV vaccine," she added.

The U.S. Food and Drug Administration (FDA) approved Arexvy for older adults in May and GSK launched it in the U.S. later in the year, ahead of the cold season.

GSK is betting on Arexvy to be its next blockbuster medicine as it grapples with a combination of patent expiries and declining revenue from its current bestsellers by the end of this decade.

($1 = 0.7918 pounds) (Writing by Ludwig Burger and Michael Erman; Editing by Kirsten Donovan and Elaine Hardcastle)