The US Food and Drug Administration has approved the GSK RSV vaccine for adults 50 to 59 years of age

RSV causes thousands of hospitalizations and deaths among older adults each year, according to Data From the Centers for Disease Control and Prevention. But the virus can also cause severe illness in adults 50 and older — or even younger — with underlying chronic conditions such as asthma, diabetes and congestive heart failure.

About 13 million Americans ages 50 to 59 are at high risk of severe illness from respiratory syncytial virus, Phil Dormitzer, head of vaccine R&D and infectious disease research at GlaxoSmithKline, said in an interview.

“It's helpful because, of course, you can meet the medical needs of that age group, but it's also nice for pharmacists to have one vaccine that they can administer to a broader population, which provides simplicity,” Dormitzer told CNBC. “.

The GSK dose will not reach this new patient population yet. A CDC advisory committee will vote later in June on recommendations for GlaxoSmithKline's vaccine, along with a competing shot from Pfizer and a newly approved shot from Moderna.

Expanded FDA approval could help GSK maintain its dominance in the RSV market later this fall and winter, when the virus begins to emerge. It usually spreads more widely In the US, the British drugmaker's shot generated around £1.2bn in sales last year, topping $890m (about £699m). In the revenue generated by the Pfizer vaccine.

GSK's chief commercial officer, Luke Mills, said on an earnings call in May that the company He stays very confident“Arexvy could generate more than £3 billion in peak annual sales over time.

Dormitzer said GSK had success in the last RSV season, but noted that the company will always take competition seriously.

He said Arexvy has shown strong efficacy in patients with underlying medical conditions.

In a late-stage trial, a single dose of the shot elicited an immune response in at-risk adults ages 50 to 59 years that was no worse than that seen in people ages 60 and older.

A previous late-stage trial in that older age group found that the vaccine was about 83% effective at preventing lower respiratory illness caused by respiratory syncytial virus (RSV) and about 94% effective at preventing severe disease.

Safety data in adults ages 50 to 59 years was also consistent with data in adults 60 and older, according to GSK. Side effects included fatigue, headache, and muscle pain, among others, which were mostly mild to moderate in severity.

A single dose of GlaxoSmithKline's vaccine was slightly less effective in adults aged 60 and older after two seasons of the virus, showing 67.2% effectiveness Against diseases of the lower respiratory tract. Dormitzer said the company will test the vaccine's effectiveness over three seasons for RSV to see if it can provide longer protection.

GSK is also considering using Arexvy in other patient groups to expand the shot in the future. The company is expected to report trial data later in 2024 in two separate groups of patients: people ages 18 to 59 who are at higher risk of severe RSV infection, and adults with compromised immune systems.

Dormitzer added that the company is also working to expand the shot in other countries. Regulatory agencies in Europe, Japan and other regions are currently reviewing GSK's application to expand Arexvy's approval to include at-risk adults aged 50 to 59 years.

A company spokesperson told CNBC that the GSK shot has been approved in nearly 50 countries.