Pfizer reveals promising phase 3 RSV vaccine results in immunocompromised adults

Pfizer has announced promising phase 3 results for its RSV vaccine, Abrysvo, specifically targeting immunocompromised adults who are at higher risk of severe RSV-related lower respiratory tract disease.

Respiratory syncytial virus (RSV) is a widespread and contagious virus that typically results in mild, cold-like symptoms. While most people recover within a week or two, the virus can cause serious illness in certain vulnerable groups, including older adults, infants, and individuals with weakened immune systems.

Pfizer’s RSV vaccine, Abrysvo, is already approved in major markets such as the United States and the European Union to protect older adults and infants via maternal immunization. However, there are no RSV vaccines currently approved in the U.S. for adults aged 18 to 59 years.

A subset of the ongoing MONeT trial was undertaken to assess the safety and immune response generated by two doses of Abrysvo, administered one month apart, in four groups of immunocompromised adults aged 18 years and older. These groups included patients with non-small cell lung cancer, those undergoing haemodialysis due to end-stage renal disease, individuals with autoimmune inflammatory disorders receiving active immunomodulator therapy, and solid organ transplant recipients.

The findings revealed that Abrysvo was well-tolerated, showcasing a safety profile in line with previous studies of the vaccine. Importantly, while Pfizer evaluated the efficacy of two doses, a single 120µg dose produced a robust neutralizing response against both RSV-A and RSV-B across all cohorts and age groups.

Pfizer plans to present these findings at an upcoming scientific conference and publish them in a peer-reviewed journal. Additionally, the company intends to submit the data to regulatory agencies for review.

Annaliesa Anderson, Pfizer’s senior vice president and chief scientific officer for vaccine research and development, commented on the results: “Immunocompromised adults, such as patients with cancer or autoimmune disorders, face a significantly increased risk of severe complications from RSV, yet there are no vaccines currently approved for those aged 18 to 59 in the U.S. We are encouraged by the positive top-line data from this study, which provide crucial evidence that Abrysvo has the potential to address a significant unmet need in this vulnerable population.”