The FDA has authorized GSK's RSV vaccine for high-risk adults aged 50 to 59, broadening its scope.

• The Food and Drug Administration broadened the use of GSK's respiratory syncytial virus vaccine to adults aged 50 to 59 who are at a higher risk of developing severe illness from the virus.
• In May 2023, the agency approved GSK's vaccine for patients aged 60 and above, who are at a higher risk of severe COVID-19 cases.
• GSK could maintain its market dominance in RSV with the FDA's expanded approval, as it competes with shots from Pfizer and Moderna.

The Food and Drug Administration (FDA) has broadened the approval of the respiratory syncytial virus (RSV) vaccine to adults aged 50 to 59 who are at a higher risk of developing severe illness from the potentially deadly virus.

The FDA has approved GSK's vaccine, Arexvy, as the first protection against RSV for the elderly population.

The Centers for Disease Control and Prevention reports that RSV causes thousands of hospitalizations and deaths among seniors annually. However, the virus can also cause severe illness in adults 50 and up, as well as younger individuals with underlying chronic conditions such as asthma, diabetes, and congestive heart failure.

GSK's head of vaccines research and development and infectious disease research, Phil Dormitzer, stated that approximately 13 million Americans aged 50 to 59 are at high risk of severe illness from RSV.

"Dormitzer explained to CNBC that the vaccine is useful not only for meeting the medical needs of that age group but also for pharmacists who can administer a single vaccine to a broader population, providing simplicity."

The CDC's advisory panel will vote on recommendations for GSK's vaccine, as well as a competitor shot and a newly approved jab, in June.

GSK's dominance in the RSV market could be maintained with the FDA's expanded approval, which is expected to occur later this fall and winter when the virus spreads more widely in the U.S. In 2020, GSK's shot generated around £1.2 billion in sales, surpassing the $890 million (about £699 million) in revenue that Pfizer's vaccine achieved.

GSK's Chief Commercial Officer, Luke Miels, stated on a May earnings call that the company is "extremely confident" that Arexvy will generate more than £3 billion in annual sales in the future.

GSK had a successful last RSV season, but Dormitzer emphasized the company's commitment to taking the competition seriously.

He said Arexvy showed strong efficacy in patients who have underlying medical conditions.

In a late-stage trial, high-risk adults aged 50 to 59 responded to a single dose of the shot with an immune response that was not worse than that seen in people aged 60 and above.

The previous trial on the older age group showed that the shot was nearly 83% effective in preventing lower respiratory tract disease caused by RSV and around 94% effective in preventing severe disease.

GSK found that safety data in adults aged 50 to 59 was consistent with data in adults aged 60 and above. The side effects reported were mostly mild to moderate in severity and included fatigue, headache, and muscle pain.

GSK's vaccine showed 67.2% efficacy against lower respiratory tract illness in adults 60 and up after two seasons of the virus. Dormitzer stated that the company will test the vaccine's efficacy over three RSV seasons to determine if it can provide even longer protection.

GSK is currently investigating Arexvy in additional patient groups to increase its effectiveness in the future. The company plans to reveal trial data for two distinct patient groups: individuals aged 18 to 59 with a higher risk of severe RSV, and adults with compromised immune systems, later in 2024.

GSK is expanding the reach of Arexvy in other countries, but regulatory agencies in Europe, Japan, and other regions are currently reviewing the company's application to expand its approval to high-risk adults aged 50 to 59.

Nearly 50 countries have approved GSK's shot, a company spokesperson informed CNBC.