# An mRNA influenza vaccine induces immunity comparable to an adjuvanted vaccine in a randomized trial

## TL;DR

An mRNA influenza vaccine was found to induce immune responses comparable to a licensed adjuvanted vaccine in a clinical trial.

## Contribution

The study demonstrates the immunogenicity of an mRNA-based influenza vaccine compared to a standard adjuvanted vaccine.

## Key findings

- Both vaccines elicited durable hemagglutination inhibition titers and increased HA-specific memory B cell responses.
- mRNA-1010 induced higher frequencies of classical and activated MBCs specific to the H3 HA strain compared to FLUAD.
- mRNA-1010 and FLUAD generated strong CD4+ T-cell responses, with a trend toward higher CD8+ T-cell responses in mRNA-1010 recipients.

## Abstract

Influenza causes substantial morbidity and mortality worldwide. This randomized, open-label, phase 1 trial (ClinicalTrials.gov, NCT05397223, date of registration: May 31, 2022) compared the immunogenicity of an mRNA-based quadrivalent influenza hemagglutinin (HA) vaccine (mRNA-1010) with a licensed comparator (FLUAD) in adults aged 18-75 years. We evaluated humoral and cellular immune responses using hemagglutination inhibition assays, flow cytometry-based memory B cell (MBC) profiling, and intracellular cytokine staining for T-cell characterization. Both vaccines elicited durable hemagglutination inhibition titers and increased HA-specific MBC responses across four vaccine strains. Compared with FLUAD, mRNA-1010 induced higher frequencies of classical and activated MBCs specific to the H3 HA included in the vaccine, while inducing similar MBC responses to the other strains. mRNA-1010 and FLUAD generated strong HA-specific CD4+ T-cell responses; a trend toward higher CD8+ T-cell responses was observed in mRNA-1010 recipients compared with FLUAD recipients for two of the four strains. These findings support the potential of the mRNA platform for seasonal influenza vaccination.