Phase 3 Trial Now Underway of Investigational mRNA-based Influenza Vaccine

The first participants have been dosed in a novel phase 3 clinical trial evaluating the efficacy, safety, and tolerability and immunogenicity of Pfizer’s quadrivalent modified RNA (modRNA) influenza vaccine candidate, announced the company last week.

The study will enroll approximately 25 000 US healthy adults aged ≥18 years.

“For years, there has been a need to better address the burden of influenza, despite the use of existing seasonal flu vaccines. Our experience with RNA viruses and mRNA technology has given us an even deeper understanding of the opportunity to potentially provide more efficacious vaccines that could further reduce the yearly rates of the severe outcomes of viral disease like flu, including hospitalization and death,” said Annaliesa Anderson, PhD, Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer, in the September 14, 2022, press release.

According to the US Centers for Disease Control and Prevention, during seasons when currently available influenza vaccine strains are similar to circulating influenza viruses, those influenza vaccines have been shown to reduce the risk of infection by approximately 40%-60%. “With circulating influenza strains continually changing, predicting the best match for the next season’s vaccine is difficult for global health experts as those strains are chosen more than six months before the start of the influenza season that they target,” stated Pfizer in the release.

The company noted that because mRNA-based vaccines only require the genetic sequence of the virus, their vaccine candidate could potentially enable more flexible, rapid manufacturing which could then lead to better influenza vaccine strain match as well as improved efficacy of currently available vaccines.

“We are excited to start the first Phase 3 efficacy study of an mRNA-based influenza vaccine that could potentially deliver an improved flu vaccine to help address the significant burden of this disease,” concluded Anderson.

The quadrivalent modRNA influenza vaccine will encode World Health Organization recommended strains for the Northern Hemisphere 2022-23 cell culture- or recombinant-based influenza vaccines, according to Pfizer. The phase 3 study is informed by previously shared data from the ongoing phase 2 clinical trial which showed “a safety and immunogenicity profile supportive of program advancement.”