TOPLINE:

Patients with severe obesity who received the recombinant influenza vaccine (RIV) showed stronger antibody responses against three influenza strains — A/H1N1, A/H3N2, and B/Yamagata — 28 days after vaccination than those who received the egg-based standard-dose vaccine, with no safety concerns observed.

METHODOLOGY:

• Researchers conducted a randomized clinical trial to compare the immunogenicity and safety profile of RIV (45 μg of recombinant hemagglutinin per strain) with that of the standard-dose (15 μg of hemagglutinin per strain) influenza vaccine in adults with severe obesity.
• A total of 206 patients with a BMI ≥ 35 (median age, 50.0 years; 60.2% women) received either RIV (n = 104) or the standard-dose vaccine (n = 102); none had been vaccinated or had a lab-confirmed influenza infection in the prior 6 months.
• Serum samples were collected at baseline and on days 28 and 180 post-vaccination; antibody responses were measured using the hemagglutination inhibition (HAI) assay.
• The primary outcome was the ratio of HAI-based on antibody titers in RIV vs standard dose groups for four influenza strains — A/H1N1, A/H3N2, B/Victoria, and B/Yamagata — on day 28.
• The secondary outcomes included antibody titers on day 180, seroconversion rates (defined as at least a fourfold increase in the HAI titers from baseline), and seroconversion factors (defined as the fold increase in the anti-HAI titers) on days 28 and 180. Safety assessments included vaccine reactogenicity by day 7 and serious adverse events.

TAKEAWAY:

• On day 28, patients who received RIV had significantly higher antibody titers than those who received the standard-dose vaccine, with ratios of 1.6 for A/H1N1, 2.0 for A/H3N2, and 1.3 for B/Yamagata (P < .05 for all).
• On day 180, there were no significant differences in antibody titers between the two groups for any strain.
• In RIV patients, seroconversion factors and seroconversion rates were significantly higher for A/H3N2 on day 28 (P < .05 for both).
• The rates of vaccine reactogenicity events were comparable between groups and mostly mild. Each group experienced three serious adverse events, with none deemed vaccine related.

IN PRACTICE:

“Our results suggest that the recombinant influenza vaccine may be preferred among adults living with obesity,” the authors wrote.

SOURCE:

The study was led by Paul Loubet, PhD, Department of Infectious and Tropical Disease at CHU Nîmes in Nîmes and University of Montpellier in Montpellier, France. It was published online on March 19, 2026, in Clinical Infectious Diseases.

LIMITATIONS:

The primary outcome assessed immune response rather than clinical efficacy. The study did not measure influenza-specific cell-mediated immunity. 

DISCLOSURES:

The trial was funded by the Programme Hospitalier de Recherche Clinique 2019 under the French Ministry of Health. Several authors disclosed having relationships with multiple pharmaceutical companies that involved receiving personal fees, nonfinancial support, travel support for scientific meetings, or consulting or lecture fees or serving roles as investigators in sponsored clinical trials.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.