Pfizer strengthens RSV shot case with data from immunocompromised adults

Pfizer has announced that its respiratory syncytial virus (RSV) vaccine, Abrysvo, has shown promising immune responses in immunocompromised adults in a late-stage study. These findings come from a subset of a Phase 3 trial managed by Pfizer, which tested two doses of Abrysvo in adults at high risk of severe lower respiratory tract disease caused by RSV. The vaccine was well-tolerated and generated a robust neutralizing response against RSV subtypes A and B.

The new data support the effectiveness of Abrysvo, which is currently competing with GSK’s Arexvy and Moderna’s mResvia. Arexvy and mResvia both received U.S. Food and Drug Administration approval in May. All three companies—Pfizer, GSK, and Moderna—are looking to extend the labeling of their respective RSV vaccines.

Presently, Abrysvo has U.S. approval for adults aged 60 and older, as well as for maternal use. In June, GSK expanded the age indication for Arexvy to include adults aged 50 to 59 who are at increased risk of RSV infection, potentially strengthening its market leadership. Moderna’s mResvia is currently approved only for adults aged 60 and older.

Pfizer has recently sought regulatory approval to extend the use of Abrysvo to at-risk adults over the age of 18, based on results from a section of the MONeT study. This part of the study focused on individuals with chronic conditions and demonstrated an immune response similar to that observed in older adults, which was the basis for Abrysvo's initial approval.

The latest data from Monday's announcement also come from the MONeT study, specifically a smaller segment that involved 203 immunocompromised adults. Participants included individuals who had received organ transplants, were undergoing hemodialysis due to end-stage kidney disease, had lung cancer, or were receiving immune-modulating treatments for autoimmune disorders. Around half of the participants were aged between 18 to 59, while the other half were 60 years or older.

Immunocompromised individuals, along with infants and the elderly, face a heightened risk of severe RSV disease, which can exacerbate underlying health conditions. Pfizer intends to present the findings from the MONeT trial at an upcoming scientific conference and publish the results in a peer-reviewed journal. Additionally, the company plans to submit the data to regulatory authorities.