On Sept. 27, 2021, Pfizer announced that the first participants have been dosed in a Phase 1 clinical trial to evaluate the safety, tolerability, and immunogenicity of a single dose quadrivalent mRNA vaccine against influenza in healthy adults.

Pfizer’s mRNA influenza vaccine program was the first in a planned wave of programs leveraging mRNA technology for influenza. Beyond influenza, the company plans to explore mRNA in other respiratory viruses.