Background:  HIV⁺ individuals have decreased response to influenza vaccine. Current US guidelines for HIV⁺ adults recommend annual immunization with a 15-µg dose of trivalent flu vaccine. There is no information about the immunogenicity of higher doses of this vaccine in HIV⁺ adults.

Methods:  We conducted a randomized, double-blinded study comparing the immunogenicity of the trivalent, inactivated, unadjuvanted, split-virus vaccine produced by Sanofi Pasteur Fluzone™ (15-µg HA per strain) vs Fluzone High-Dose™ (HD; 60 µg/strain) in HIV⁺ adults attending a single clinic in the University of Pennsylvania, Philadelphia. We measured A/California/07/2009 (H1N1), A/Victoria/210/2009 (H3N2), and B/Brisbane/60/2008 antibody titers using the hemagglutination-inhibition (HAI) assay.

Results:  Of 195 participants enrolled in the trial, 190 (93 Fluzone™, 97 HD) completed the 3-week follow-up visit:  71% were male, 68% African American, median age was 45 (range 20 to 78) years; 89% were on HAART, with a median current CD4⁺ count of 452 (IQR 293 to 629) cells/mm³, and a nadir CD4 of 180 (IQR 53 to 318) cells/mm³. The HIV RNA viral load was <200 copies/mL in 89% of the subjects receiving treatment. Approximately half the patients had protective titers at baseline. By week 3, geometric mean antibody titers and the proportion of individuals with protective HAI titers were higher in participants vaccinated with the HD. Both vaccines were well tolerated, with 165 adverse events (77 Fluzone™ vs 88 HD, p = ns). Grade 1 myalgia (19%), malaise (14%), local pain (10%), local tenderness (10%), and headache (9%) were the most frequent adverse events. There were no serious adverse events.

Serological results

Conclusions:  Patients with HIV infection reach higher levels of protection if vaccinated with a single dose of Fluzone High-Dose™ vs standard trivalent vaccine. High-dose vaccine may be preferred when vaccinating HIV⁺ individuals against seasonal flu.