Recombinant vs Standard Influenza Vaccine in Adults With Severe Obesity: A Randomized Clinical Trial

Individuals with severe obesity are at increased risk of severe influenza and may have impaired immune responses to vaccination. Recombinant influenza vaccine (RIV) may provide enhanced protection compared with egg-based standard-dose influenza vaccine (SD), but data in this high-risk population are limited.

The AP-HP FLUO trial (NCT05409612) was an open-label, randomized clinical trial conducted in 15 centers in France (November 2022-March 2023) with 6 months of follow-up. Adults with BMI ≥35 kg/m2 were randomized 1:1 to receive RIV or SD, using minimization by center, age (<50 vs ≥50 years), and BMI (<40 vs ≥40 kg/m2). The primary outcome was the ratio (RIV/SD) of geometric mean hemagglutinin-inhibition (HAI) titers (GMTs) for 4 influenza strains 28 days after vaccination. Safety and reactogenicity were also assessed.

A total of 206 participants were included (104 RIV, 102 SD). Median age was 50 years, 60.2% were women, and median BMI was 41.0 kg/m2. At Day 28, GMT ratios favored RIV for A/H1N1 (1.6; 95% CI, 1.1-2.3), A/H3N2 (2.0; 95% CI, 1.3-3.2), and B/Yamagata (1.3; 95% CI, 1.0-1.8), but not for B/Victoria (0.9; 95% CI, 0.6-1.3). The effect did not vary significantly across the different age and BMI groups. By Day 180, titers did not differ significantly. Reactogenicity and safety profiles were similar between groups.

In adults with severe obesity, RIV elicited stronger short-term humoral immune responses than an egg-based standard-dose vaccine, suggesting potential additional benefit for influenza prevention in this vulnerable population.