Background: HIV-infected persons have less robust antibody responses to influenza vaccines.
Objective: To compare the immunogenicity of high-dose influenza vaccine with that of standard dosing in HIV-positive participants.
Design: Randomized, double-blind, controlled trial. (ClinicalTrials.gov: NCT01262846)
Setting: The MacGregor Clinic of the Hospital of the University of Pennsylvania, Philadelphia, from 27 October 2010 to 27 March 2011.
Participants: HIV-infected persons older than 18 years.
Intervention: Participants were randomly assigned to receive either a standard dose (15 mcg of antigen per strain) or a high dose (60 mcg/strain) of the influenza trivalent vaccine.
Measurements: The primary end point was the rate of seroprotection, defined as antibody titers of 1:40 or greater on the hemagglutination inhibition assay 21 to 28 days after vaccination. The primary safety end point was frequency and intensity of adverse events. Secondary end points were seroconversion rate (defined as a greater than 4-fold increase in antibody titers) and the geometric mean antibody titer.
Results: 195 participants enrolled, and 190 completed the study (93 in the standard-dose group and 97 in the high-dose group). The seroprotection rates after vaccination were higher in the high-dose group for the H1N1 (96% vs. 87%; treatment difference, 9 percentage points [95% CI, 1 to 17 percentage points]; P = 0.029), H3N2 (96% vs. 92%; treatment difference, 3 percentage points [CI, -3 to 10 percentage points]; P = 0.32), and influenza B (91% vs. 80%; treatment difference, 11 percentage points [CI, 1 to 21 percentage points]; P = 0.030) strains. Both vaccines were well-tolerated, with myalgia (19%), malaise (14%), and local pain (10%) the most frequent adverse events.
Limitations: The effectiveness of the vaccine in preventing clinical influenza was not evaluated. The number of participants with CD4 counts less than 0.200 × 109 cells/L was limited.
Conclusion: HIV-infected persons reach higher levels of influenza seroprotection if vaccinated with the high-dose trivalent vaccine than with the standard-dose.
Primary funding source: National Institute of Allergy and Infectious Diseases and Center for AIDS Research of the University of Pennsylvania.