Dive Brief:

• Shares of Moderna, Pfizer and GSK fell as advisers to the Centers for Disease Control and Prevention discussed updated guidelines for RSV vaccination at a Wednesday meeting.
• The expert panel recommended adults over 75 years should receive a shot for RSV, or respiratory syncytial virus, as should those between 60 and 74 years who are at higher risk of severe disease. The recommendation, which the CDC adopted, replaces the shared clinical decision-making guidance for all adults over 60 that was put in place last year. 
• The committee postponed discussion of vaccine recommendations for adults aged 50 to 59 years old, which could potentially delay GSK’s plans to expand its shot’s use in that age group after a recent Food and Drug Administration approval.

Dive Insight:

The new vaccination recommendations could shape the market for RSV shots in the U.S. Notably, the CDC is not yet recommending that anyone who previously was vaccinated for RSV get another dose. 

The guidelines for adults between 60 and 74 years old are now more narrow. While people in this age group who are not high risk of RSV disease can still get a vaccine, the changed recommendations might affect whether a shot is covered by insurance. The list of relevant risk factors is broad, however, including cardiovascular disease, lung disease and neurologic or neuromuscular conditions.

Committee members also reviewed at the Wednesday meeting safety data on a neurological side effect called Guillain-Barré syndrome, or GBS, that’s been reported in very rare cases following vaccination GSK’s Arexvy and Pfizer’s Abrysvo. No cases have been reported with Moderna’s newer vaccine Mresvia.

While the rate associated with Abrysvo was higher than with Arexvy, an FDA presentation noted that the analyses were “mixed and highly uncertain.” Still, Evercore ISI analyst Umer Raffat wrote that the advisers gave a “huge pass” to Pfizer. 

Shares in Moderna were hit particularly hard as the company presented updated data on its shot’s efficacy over time. After 18 months, Mresvia’s protection against RSV disease with two or more symptoms fell to 50%, lower than with GSK’s Abrysvo. 

Moderna has been banking on winning a share of the market with its mRNA-based shot, which is available as a more convenient pre-filled syrigne. The vaccine was approved in May.