(Reuters) - U.S. sales of RSV vaccines from GSK and Pfizer are down significantly after regulators narrowed the targeted age group and said it was a once-in-a-lifetime shot for now, excluding millions of people who got one last year.

Pfizer on Monday won a bid in a London court to invalidate two of GSK's patents relating to a respiratory syncytial virus (RSV) vaccine. The two pharmaceutical giants are among a number of companies in competition for a vaccine for RSV,

The UK High Court has ruled that two GSK respiratory syncytial virus (RSV) vaccine patents are invalid in an action involving Pfizer, as both companies battle to become the first to launch an RSV vaccine on the UK market.

This is the first RSV vaccine approved in Singapore for use in older adults and pregnant individuals, providing critical protection to infants and seniors

U.S. sales of RSV vaccines from GSK and Pfizer are down significantly after regulators narrowed the targeted age group and said it was a once-in-a-lifetime shot for now, excluding millions of people who got one last year.

Pfizer (NYSE:PFE) has reportedly succeeded in getting a U.K. court to invalidate two of GSK’s (NYSE:GSK) patents for its RSV vaccine. The ruling is part of ongoing litigation between the two drugmakers over their respective RSV vaccines.