Sanofi Pasteur and Translate Bio have initiated a Phase 1 clinical trial evaluating an mRNA-based investigational vaccine against seasonal influenza. The trial will evaluate the safety and immunogenicity of a monovalent flu vaccine candidate coding for the hemagglutinin protein of the A/H3N2 strain of the influenza virus. Flu seasons that are dominated by A/H3N2 strain circulation activity tend to be more severe, especially among those considered at-risk such as older adults and younger children.

Sanofi and Translate Bio have developed and will evaluate two formulations of the vaccine (MRT5400 and MRT5401) in the Phase 1 influenza mRNA vaccine clinical trial. The two formulations differ in the lipid nanoparticle (LNP) that contains the mRNA. The trial follows successful preclinical research which demonstrated promising safety and immunogenicity.

Preclinical results were shared previously at the 8th annual mRNA Healthcare Conference in November 2020. The US-based Phase 1 clinical trial will assess the safety and immunogenicity (immune response) of the monov lent (single-strain) mRNA-based flu vaccine candidate in up to 280 participants. The trial will evaluate several dose levels of both vaccine formulations given to healthy adults 18 - 49 years of age.