In a significant development, the Food and Drug Administration (FDA) expanded the approval of GlaxoSmithKline's (GSK) respiratory syncytial virus (RSV) vaccine to include adults between the ages of 50 and 59 who are at an increased risk of severe illness from the virus. The FDA had initially approved GSK's jab in May 2023 for patients aged 60 and above.

GSK's vaccine, named Arexvy, is now the first vaccine authorized by the FDA to specifically protect this high-risk population from RSV. RSV is responsible for numerous hospitalizations and deaths among seniors each year, as highlighted by data from the Centers for Disease Control and Prevention (CDC). However, the virus can also cause severe illness in adults aged 50 and older who have underlying chronic conditions such as asthma, diabetes, and congestive heart failure.

According to Phil Dormitzer, GSK's head of vaccines research and development and infectious disease research, approximately 13 million Americans between the ages of 50 and 59 fall into the high-risk category for severe RSV illness. This expanded approval not only addresses the medical needs of this age group but also provides greater convenience for pharmacists, who now have a single vaccine to administer to a wider population.

While GSK's shot is yet to reach this new patient population, an advisory panel to the CDC is expected to vote on recommendations for GSK's vaccine, along with rival shots from Pfizer and Moderna, later in June. The expanded FDA approval could give GSK an edge in maintaining its dominance in the RSV market during the upcoming fall and winter seasons, when the virus typically spreads more widely in the United States.

Last year, GSK's RSV vaccine generated around £1.2 billion in sales, outperforming Pfizer's vaccine, which brought in approximately $890 million in revenue. GSK's Chief Commercial Officer, Luke Miels, expressed confidence during an earnings call in May that Arexvy has the potential to achieve peak annual sales exceeding £3 billion.

Dormitzer highlighted the strong efficacy of Arexvy in patients with underlying medical conditions, citing results from late-stage trials. A single dose of the vaccine in high-risk adults aged 50 to 59 elicited an immune response similar to that observed in patients aged 60 and above. Previous late-stage trials showed the shot to be nearly 83% effective in preventing lower respiratory tract disease caused by RSV and about 94% effective in preventing severe disease.

Safety data for Arexvy in adults aged 50 to 59 aligned with the data observed in adults aged 60 and above, with mostly mild to moderate side effects reported, including fatigue, headache, and muscle pain.

Looking forward, GSK plans to test the vaccine's efficacy over three RSV seasons to determine if it can provide extended protection. The company is also conducting studies to expand the reach of Arexvy in other patient groups, including individuals aged 18 to 59 at high risk of severe RSV and adults with weakened immune systems. Furthermore, GSK is pursuing regulatory approvals in Europe, Japan, and other countries to widen the availability of Arexvy for high-risk adults aged 50 to 59.

With its expanded approval and ongoing efforts to expand its reach globally, GSK is poised to maintain its prominent position in the competitive RSV market.