Pfizer RSV vaccine may protect high-risk adults ages 18-59

A vaccine of Pfizer showed the potential to protect adults ages 18 to 59 who are at increased risk of becoming seriously ill from respiratory syncytial virus in a late-stage clinical trial, the company announced Tuesday.

Initial data suggests that Pfizer’s vaccine, known as Abrysvo, could help protect a much broader population against RSV. The vaccine is currently approved in the United States, Europe, Japan and other countries for adults aged 60 and older and pregnant women who can pass protection to their fetus.

But there are no approved RSV vaccines globally for younger, high-risk adults.

RSV causes thousands of hospitalizations and deaths among older Americans and hundreds of infants each year. The virus can also cause serious illness in young adults who have weakened immune systems or who have underlying chronic illnesses such as asthma and diabetes.

Nearly 10% of U.S. adults ages 18 to 49 have a chronic condition that puts them at serious risk for RSV disease, according to Pfizer. This figure rises to around 24% for those aged 50 to 64.

“I think of my own family and friends who have asthma or who had illnesses since childhood,” Dr. Iona Munjal, executive director of clinical vaccine research and development at Pfizer, told CNBC. “This population is at risk of contracting RSV every winter…again and again. There is no lasting immunity without vaccination.”

Munjal added that high-risk adults ages 18 to 59 are the “logical next step” after working to reduce RSV disease rates in older populations.

The data comes as Pfizer attempts to gain more share of the RSV market after falling behind. GlaxoSmithKline Last year. GSK’s RSV vaccine for adults aged 60 and over recorded sales of around £1.2 billion ($1.5 billion) last year. Meanwhile, Pfizer’s vaccine recorded revenue of around $890 million in 2023.

Pfizer said it plans to submit the data to regulatory agencies and seek expanded approval of Abrysvo for those 18 and older. The company did not provide any details on the timing of these plans.

Pfizer also intends to present the final results of the trial at an upcoming scientific conference and submit them for publication in a peer-reviewed journal.

Pfizer said Tuesday its vaccine met the phase three trial’s primary endpoints for effectiveness and safety in high-risk adults ages 50 to 59.

The company specifically released data from a substudy examining nearly 700 patients at high risk for severe RSV due to underlying medical conditions. Pfizer plans to release data on another substudy of about 200 patients with compromised immune systems later this year, Munjal told CNBC.

According to the results, a single dose of the pharmaceutical manufacturer’s vaccine caused an immune response against RSV A and RSV B, which are the two main subtypes of the virus.

The immune response was similar to that seen in adults 60 years and older. Previous late-stage research on more than 30,000 adults in this older age group found that the Pfizer shot maintained protection against RSV for two full seasons of the virus.

“The level of antibodies that you see after vaccination in people aged 18 to 60 is similar to that of people aged 60 and older,” Munjal told CNBC. She later added that this “gives you confidence that in these two populations, they are in fact responding the same way to the vaccine and therefore are likely to have similar effectiveness.”

Participants also saw a four-fold increase in their levels of protective antibodies against RSV A and RSV B one month after receiving the Pfizer vaccine compared to before vaccination.

The company said patients tolerated the vaccine well in the trial. Safety data in high-risk adults ages 18 to 59 were consistent with findings in adults 60 and older, Pfizer added.

GSK released late-stage trial data in October suggesting its vaccine could protect adults aged 50 to 59.

In February, the Food and Drug Administration granted “priority review” to GSK’s application to expand approval of its drug, Arexvy, to this new age group. This designation speeds up the review process for certain drugs intended to treat serious conditions.

The FDA is expected to decide whether to approve GSK’s RSV vaccine for adults ages 50 to 59 on June 7.