Investigators conducted a randomized, single-blinded, controlled trial comparing high-dose IIV4 (60 μg, Efluelda, Sanofi) with standard-dose IIV4 (15 μg, Vaxigrip Tetra, Sanofi). Vaccinations were administered between August and December 2023. Seroprotection (SP) was prespecified as a hemagglutination-inhibition antibody titer ≥1:40 measured one month after vaccination. The trial enrolled 110 participants; 103 met per-protocol criteria and were analyzed (52 in the high-dose group and 51 in the standard-dose group). The cohort had a mean age of 49.6 years and was 63.1% male. Median CD4 count was 555 cells/mm3. Most participants were virologically suppressed (93.2%), and 57.3% were receiving integrase inhibitor–based antiretroviral therapy.
Short, practical facts: the study focused on adults living with HIV (PLWH) and used established serologic endpoints. The single-blind design meant participants were unaware of dose allocation, while investigators retained allocation knowledge as described by the authors.
Overall, 50.5% of participants achieved seroprotection to all four vaccine strains at one month post-vaccination. The high-dose IIV4 group exhibited higher overall seroprotection compared with the standard-dose IIV4 group: 61.5% versus 39.2% (p = 0.02), the authors reported. Strain-specific analyses revealed a statistically significant advantage for the A/H3N2 component: seroprotection rates were 76.9% in the high-dose arm and 52.9% in the standard-dose arm (p = 0.01).
The paper supplied these comparative immunogenicity results without additional subgroup breakdowns beyond the variables reported. The investigators framed the seroprotection endpoint in the conventional hemagglutination-inhibition context used in influenza vaccine studies.
The study team performed multivariable logistic regression to identify factors independently associated with achieving seroprotection against all four strains. Receiving high-dose IIV4 was associated with higher odds of seroprotection (odds ratio [OR] 2.7; 95% CI 1.9–6.1; p = 0.02). Female sex was also an independent predictor (OR 2.5; 95% CI 1.1–5.9; p = 0.04), according to the authors. Those were the covariates reported as statistically significant; the abstract did not list additional model covariates or report model diagnostics.
The reported associations indicate that dose and sex were influential in serologic response within this cohort of PLWH, but the source did not provide full model specification details in the abstract. Any interpretation should therefore refer to the full text for complete multivariable model parameters.
Adverse events (AEs) were actively monitored in the trial. Overall AE rates were similar between groups: 55.8% of participants in the high-dose arm reported adverse events compared with 58.8% in the standard-dose arm (p = 0.75). Local reactions were the most commonly reported events. The authors noted that no severe vaccine-related events occurred during the observation window reported in the abstract.
Concise takeaways: higher antigen content in the high-dose formulation increased serologic responses for at least one strain without a measurable increase in reactogenicity or severe events in this trial population.
The abstract reported key outcomes but omitted several granular details. The source did not provide, within the abstract, the full list of variables included in multivariable models, per-strain geometric mean titer fold-rise data, or longer-term durability of antibody responses beyond the one-month post-vaccination timepoint. Clinical effectiveness outcomes—such as laboratory-confirmed influenza illness, hospitalization, or real-world vaccine effectiveness—were not reported and remain unassessed in this paper. The authors recommended further investigation into clinical effectiveness and noted the trial registration number (TCTR20230501002).
Those unanswered questions frame the immediate next steps: confirm whether the immunologic advantages observed, particularly for A/H3N2, translate into fewer influenza cases or complications among PLWH, and evaluate durability of protection and broader subgroup effects in larger or longer trials.