08:39 AM EDT, 08/16/2024 (MT Newswires) -- (Updates with missed target, stock movement in headline and lead paragraph, and additional details.)

Shares of BioNTech (BNTX) were down 4% in Friday's premarket session after the biotech firm and Pfizer ( PFE ) reported that their phase 3 study assessing a combined mRNA vaccine candidate targeting influenza and COVID-19 missed one of two primary immunogenicity targets.

The two primary immunogenicity objectives of the trial measured immunogenicity against SARS-CoV-2 and immunogenicity against influenza A and B. The companies said the trial did not meet the primary immunogenicity objectives of non-inferiority against the influenza B strain.

In a statement, BioNTech and Pfizer ( PFE ) said they "are evaluating adjustments to the combination vaccine candidate aimed at improving immune responses against influenza B and will discuss next steps with health authorities."

The trial, which involved over 8,000 participants 18 to 64 years of age, aimed to assess the safety, tolerability, and immunogenicity of a single-dose combination vaccine candidate versus a licensed influenza vaccine and their licensed COVID-19 vaccine given at the same visit, the companies said.

The formulation showed "higher influenza A responses versus a licensed influenza vaccine" and "comparable responses" against SARS-CoV-2 compared with the companies' licensed COVID-19 vaccine, they added.

Pfizer's ( PFE ) phase 2 trial of a second-generation mRNA-based influenza vaccine also demonstrated "robust immunogenicity" against both influenza and COVID-19 and that no safety signals were identified, according to the companies' joint release.

Price: 28.65, Change: -0.06, Percent Change: -0.23