On Friday, Pfizer Inc. (PFE  ) and BioNTech SE (BNTX  ) released topline results from the Phase 3 trial of the combined mRNA vaccine candidate against influenza and COVID-19 in healthy individuals 18-64 years of age.

The combination candidate comprises Pfizer's mRNA-based influenza vaccine candidate with the companies' licensed COVID-19 vaccine.

The Phase 3 trial measured two primary immunogenicity objectives (immunogenicity against SARS-CoV-2 and immunogenicity against influenza A and B), of which one was met.

Compared to a licensed influenza vaccine, the trivalent (tIRV) formulation demonstrated influenza A responses, including a continued trend of higher influenza A responses versus a licensed influenza vaccine, while it showed lower geometric mean titers and seroconversion (the time between exposure to a virus and when antibodies show up in the blood) against the influenza B strain.

In addition, the formulation demonstrated comparable responses against SARS-CoV-2 versus the companies' licensed COVID-19 vaccine.

An ongoing safety data review has not identified any safety signals with the combination vaccine.

The companies are evaluating adjustments to the combination vaccine candidate to improve immune responses against influenza B and will discuss the next steps with health authorities.

The Phase 3 study enrolled 8,000 participants.

The setback comes after Moderna Inc. (MRNA  ) released positive Phase 3 trial data for its combination vaccine against Influenza and COVID-19 in June.

In a separate Phase 2 trial, Pfizer evaluated trivalent (tIRV) influenza mRNA standalone vaccine candidates, demonstrating robust immunogenicity in individuals aged 18 to 64.

Last year, Pfizer announced topline Phase 3 results from its first-generation quadrivalent (qIRV) vaccine candidate, which achieved the first and only demonstration of efficacy for an mRNA vaccine in a group of study participants aged 18- 64.

The primary endpoints for this first-generation candidate were not met in adults aged 65 and older, as statistical non-inferior relative vaccine efficacy compared to a licensed influenza vaccine was not met based on the number of cases accrued.

Pfizer developed second-generation candidates to improve immunogenicity.

The tIRV formulations elicited robust influenza A and B responses, including a continued trend of higher influenza A responses compared to a licensed influenza vaccine.

No safety signals were reported. Data from the Phase 2 trial for adults 65 and older will become available later.

Pfizer will also continue to evaluate its influenza vaccine program and discuss next steps with health authorities.

Price Action: BNTX stock is down 3.72% at $84.00, and PFE stock is down 0.03% at $28.70 during the premarket session at last check Friday.