GSK shares fall as US narrows age recommendation for RSV vaccines

GSK shares fell more than 6 per cent on Thursday morning after US health officials recommended restricting the use of vaccines for respiratory syncytial virus, an area in which the British pharmaceutical group is the market leader.

GSK received approval from the US Food and Drug Administration in June to expand the use of its blockbuster Arexvy vaccine from those aged over 60 to those aged 50 to 59.

Last year, the US Centers for Disease Control and Prevention recommended the jabs for individuals aged over 60. After reviewing the data, a CDC committee said on Wednesday that RSV vaccinations should be given routinely to the over-75s.

However, for those aged between 60-74 it said jabs should be limited only to those at risk of severe RSV, reducing the number of patients who can receive a vaccine in this age group. 

The CDC committee also postponed a decision on recommending RSV vaccine use for those aged between 50 and 59, citing a need for more data. The move deals a blow to GSK as vaccinations for the seasonal virus, which causes flu-like symptoms, are expected to increase in late summer and autumn. 

GSK shares fell by more than 6 per cent in early trading in London before paring some of those losses.

According to figures cited by GSK, the virus causes approximately 42,000 hospitalisations a year in adults aged between 50 and 64.

GSK’s Arexvy vaccine was launched in 2023 and generated more than £1bn in sales in its first year of use, after it was recommended for over-60s by the FDA.

The rollout of the vaccine has been considered a success for GSK, as it accounted for more than two-thirds of doses given in the first inoculation season, beating its rival Pfizer.

But it received a blow in the UK after the government awarded an RSV vaccine contract to Pfizer at the start of June.

Moderna recently received FDA approval for a rival vaccine. But it presented data to the CDC on Wednesday showing that its jab provided much weaker protection than GSK and Pfizer’s after 18 months, causing shares to fall 11 per cent on Tuesday.

Analysts had expected up to £3bn in peak annual sales for Arexvy and $3.6bn for Pfizer’s rival jab Abrysvo, but Peter Verdult, an analyst at Citi said he expected peak sales to “fall materially” for Arexvy and as a result of the CDC’s decision.