The drugmaker is racing rival Pfizer Inc to introduce the first approved RSV vaccine in the United States, where 14,000 people die annually of the lower respiratory tract disease caused by the virus.

Last week, a panel of outside advisers to the U.S. Food and Drug Administration held separate votes on the two vaccines and backed both. The FDA is scheduled to make an approval decision on the vaccines by May, and typically follows the panel's recommendations.

"We are ready to launch without capacity or supply constraints... to supply the market that we see," Phil Dormitzer, who oversees R&D for vaccines at GSK, said in an interview on Wednesday.

GSK has already produced much of the vaccine components it anticipates needing for that launch, mainly at its plant in Wavre, Belgium, he added.

The drugmaker published late-stage data in October showing its vaccine to be 82.6% effective in preventing lower respiratory tract disease in people aged 60 and over.

GSK's data also showed similar efficacy for sub groups such as people with other health issues, Dormitzer said. "I think that consistency may give us an advantage."

Pfizer's vaccine was 85.7% effective among participants with three or more symptoms, and 66.7% for two or more symptoms, according to an interim analysis of its pivotal clinical trial in the same age group.

Another possible advantage revealed in GSK's data was strong efficacy when its RSV shot is jointly administered with a flu vaccine, added Dormitzer, who joined GSK in late 2021 from Pfizer, where he helped develop and launch its COVID-19 vaccine with partner BioNTech.

Pfizer has not published data on RSV/flu co-administration.

GSK also sees China as an important future market for the vaccine, Dormitzer said. He cited "tremendous interest" in the company's shingles vaccine Shingrix there. China contributed strongly to record Shingrix sales last year of 3 billion pounds ($3.55 billion).

GSK Chief Executive Emma Walmsley said in January the company is confident its RSV vaccine has "multibillion-pound Shingrix-like annual potential."

The company has yet to apply for approval in China for the RSV vaccine but has had the country's specific requirements for entry in mind during development, Dormitzer said.

GSK has applied for regulatory approval in the European Union and Japan.

Competition with Pfizer's RSV vaccine could boost public awareness of the virus' disease burden, Dormitzer said, noting how the pandemic showed the importance of such education.

"High efficacy is not enough for people to choose to take the vaccine," he said.

($1 = 0.8449 pounds)

(Reporting by Maggie Fick; Editing by Bill Berkrot)

By Maggie Fick