Intranasal Flu Vaccine Coadministered with High-Dose Shot in Older Adults Superior Over Shot Alone: Daily Dose

_{©New Africa/AdobeStock}

Patient Care brings primary care clinicians a lot of medical news every day—it’s easy to miss an important study. The Daily Dose provides a concise summary of one of the website's leading stories you may not have seen.

On July 15, 2024, we reported on findings from a study published in Lancet Infectious Diseases that evaluated the safety and immunogenicity of the intranasal H3N2 M2-deficient single-replication (M2SR) vaccine, alone or coadministered with an inactivated influenza vaccine (Fluzone High-Dose Quadrivalent [Fluzone HD]).

The study

Investigators enrolled 300 adults aged 65 to 85 years who were considered healthy or who had stable chronic conditions and had not received influenza vaccinations in the past 6 months. Participants were randomly assigned (3:3:3:1)to receive the intranasal H3N2 M2SR vaccine with Fluzone HD, H3N2 M2SR with placebo, Fluzone HD with placebo, or placebo alone. The primary outcome assessed the safety of H3N2 M2SR, both alone and in combination with Fluzone HD and secondary endpoints assessed serum and mucosal antibody levels. Enrollment and randomization took place between June 14 and September 15, 2022.

The findings

The researchers reported that coadministration of H3N2 M2SR vaccine with Fluzone-HD in the elderly cohort was well tolerated with only 2% to 5% of participants across all groups reporting any treatment-emergent adverse events. They found that intranasal H3N2 M2SR with Fluzone HD induced seroconversion (4-fold or greater increase in hemagglutination inhibition antibodies from baseline to day 29) in 44 (48%) of 91 participants, compared with 28 (31%) of 90 participants who seroconverted in the Fluzone HD plus placebo group (P = .023). H3N2 M2SR with Fluzone HD also induced mucosal and cellular immune responses.

Authors' comment

“If H5N1 or any other mutating influenza strain were to begin infecting millions of people as SARS-CoV-2 did, imagine the benefits of combining an intranasal vaccine, which could stop most infections from occurring, with a strong antibody-based vaccine shot. The impact on human health could be unequalled in our history.”

Click here for more details.