Phase 4 randomized trial of intradermal low-antigen-content inactivated influenza vaccine vs. standard-dose intramuscular vaccine in HIV-1-infected adults

This study evaluated safety, tolerability and immunogenicity of intradermal (ID) trivalent inactivated split influenza vaccine, with a lower antigen content (9 mu g HA per strain) than the conventional intramuscular one (15 mu g), in HIV-1-infected adults younger than 60 y. A total of 54 HIV-1-positive participants were enrolled and randomly assigned to receive a single dose of either ID-administered low-antigen-content split inactivated vaccine or intramuscularly-administered (IM) standard-dose inactivated split vaccine. Subjects were provided with a diary to monitor any local and/or systemic reactions to the vaccine for 7 d following vaccination. Serum samples were collected before, 28 d and 90 d after immunization. The plasma HIV-RNA and CD4(+) T-lymphocyte count were checked at day 0 and day 90. Serum hemagglutination-inhibition (HI) activity for the three influenza strains included in the vaccine composition was measured to assess the antibody response at one month and 3 mo after vaccination. Both vaccines showed optimal safety and tolerability profiles. All the three Committee for Medicinal Products for Human Use immunogenicity criteria for vaccine approval in adults younger than 60 were met by both vaccines against A(H1N1) and A(H3N2) viruses. Both vaccines met mean-fold-increase and seroprotection criteria but failed seroconversion criteria against B virus. No difference in terms of post-vaccination geometric mean titers, mean fold increase, seroprotection and seroconversion rates were found comparing ID and IM vaccines. In conclusion, the recently available low-antigen-content ID vaccine is safe, well-tolerated and as immunogenic as IM standard-dose influenza vaccine.