Background:  HIV-infected patients have weaker antibody responses after influenza vaccination than healthy controls. Intracutaneous vaccination is dose sparing and has potential immunologic benefits. We studied the serological response upon intramuscular or intracutaneous influenza vaccination in both HIV-infected patients and healthy controls in a randomized, prospective, open-label study.

Methods:  In the fall of 2005, we vaccinated 80 HIV-infected patients and 41 age-matched healthy controls with a trivalent subunit influenza vaccine (Influvac 2005/06). Subjects were randomized to receive either the standard dose (0.5 mL) by intramuscular vaccination (41 HIV-infected patients with a mean CD4 count of 440 per µliter and 20 healthy controls) or 0.1 mL intracutaneously (39 HIV-infected patients with a mean CD4 count of 486/µL and 21 healthy controls). Hemagglutination inhibition titres were measured on days 0 and 30.

Results:  After (standard) intramuscular vaccination, HIV-infected patients had significantly lower postvaccination titres than healthy controls. In HIV-infected patients, intracutaneous vaccination was equal or superior to intramuscular vaccination, irrespective of the CD4 count. This trend was most evident in patients who had already been vaccinated in 2003 and/or 2004 (compared to those who had never before received an influenza vaccination), although significant only for influenza B in this subgroup (p <0.05, ANOVA). Local skin reactions to the intracutaneous vaccine were mild and significantly less frequently reported by HIV-infected patients (45%) than healthy controls (84%, p <0.05, χ² test).

Conclusions:  We draw 3 conclusions:  Intracutaneous influenza vaccination leads to equal or higher postvaccination titres compared to standard intramuscular vaccination in HIV-infected patients. Local skin reactions were less frequent and less severe in HIV-infected patients than in healthy controls. The benefits of dose-sparing intracutaneous influenza vaccination are most apparent in HIV patients who were vaccinated at least once in the years prior to our study.