RSV Vaccine for People 18 to 59 Years Posts Positive Phase 3 Results

Pfizer Inc. today reported encouraging top-line data regarding the safety and immunogenicity of its ABRYSVO® vaccine from an ongoing Phase 3 clinical trial.

The study (NCT05842967) has been evaluating the effectiveness of a single dose of the vaccine compared to a placebo in adults between the ages of 18 and 59 who are at risk of developing severe lower respiratory tract disease associated with respiratory syncytial virus (RSV). 

On April 8, 2024, Pfizer confirmed the MONeT study achieved its co-primary immunogenicity endpoints and primary safety endpoint:

• Participants demonstrated RSV-A and RSV-B subgroup neutralizing responses non-inferior to the response seen in the Phase 3 RENOIR study of ABRYSVO in more than 34,000 adults aged 60 or older where vaccine efficacy was previously demonstrated.
• Participants also achieved at least a four-fold increase in serum neutralizing titers for RSV-A and RSV-B one month after receiving ABRYSVO compared to pre-vaccination.
• During the trial, ABRYSVO was well-tolerated, and safety findings were consistent with those from previous investigations of ABRYSVO in other populations.

Pfizer stated it intends to submit these data to regulatory agencies and request expansion of the age group from the current indication to 18 years of age and older.

This is an essential study since no RSV vaccines were approved for adults in this age group during the 2023-2024 RSV season.

“These encouraging results provide evidence that ABRYSVO can help protect adults with increased risk against RSV-associated illness,” said Annaliesa Anderson, Ph.D., Senior Vice President and Head, Vaccine Research and Development, Pfizer, in a press release.

“We are excited to address a significant unmet need, pending regulatory authority approval, as ABRYSVO has the potential to become the first and only RSV vaccine for adults 18 years and older.”

As of April 5, 2024, RSV vaccines have been approved in Canada, Europe, Japan, the United States, and the United Kingdom.

The U.S. CDC estimates the percentage of adults 60+ vaccinated this season was 23.6%. And RSVVaxView reported that the overall RSV vaccination rate among pregnant women was about 18%.