GSK sign with needle in foreground
GSK beats third quarter estimates and raises guidance / Image source: Adobe
  • US Centre for Disease Control restricts vaccine use
  • Decision could limit vaccine sales
  • GSK has a leading market share in RSV vaccines

Shares in GSK (GSK) were marked down 5% to £15.16 after the US CDC (Centre for Disease Control) advised a narrower use of RSV (respiratory syncytial virus) vaccines, cutting the potential market for GSK’s leading Arexvy vaccine.

The drop eradicates most the year’s gains leaving the shares up 3% compared with a 6% gain in the blue-chip FTSE 100 index.


The CDC’s advisory committee on immunisation practices voted unanimously to restrict RSV vaccine recommendation to the at-risk 60 to 74 age group and expand use for the over 75s.

Jefferies analyst Peter Welford believes the decision may cut GSK’s addressable market from around 80 million people aged over 60 and another 13 million aged 50 to 59 to circa 55 million.

The CDC’s decision is disappointing given that GSK gained FDA (Food and Drug Administration) approval for Arexvy in the prevention of RSV in adults aged 50 to 59 who are at increased risk on 10 June, the first vaccine to be endorsed for that age group.

Shore Capital analyst Sean Conroy pointed out the decision does not preclude recommendations being more permissive once further efficacy and safety data has been accumulated.

GSK expects to announce results of trials in adults aged 18 to 49 at increased risk, and immunocompromised adults aged 18 and over, in the second half of 2024.

GSK’s Arexvy and Pfizer’s (PFE:NYSE) Abrysvo are the leading RSV vaccines with the former holding around two thirds of the new RSV vaccine market. It generated £1.2 billion of revenue for GSK in 2023.

Biotechnology company Moderna (MRNA:NASDAQ) received US regulatory approval for its RSV vaccine on 31 May. Moderna shares fell 5% yesterday (26 June) after the company revealed its RSV shot only showed 50% efficacy after 18 months and 47.4% after 24 months, compared with 78% for both GSK’s and Pfizer’s shot.


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Issue Date: 27 Jun 2024