Higher Antigen Content Improves the Immune Response to 2009 H1N1 Influenza Vaccine in HIV-Infected Adults: A Randomized Clinical Trial.

Background. The immunogenicity of a high hemagglutinin (HA) dose or a second dose of influenza vaccine in human immunodeficiency virus (HIV)-infected individuals has not been fully explored. Methods. One hundered ninety-two HIV-infected individuals aged 18-64 years were stratified by CD4 cell count (<200 cells/mL or ≤200 cells/mL) and randomized to receive 2 doses of 15 μg or 30 μg HA 2009 H1N1 vaccine 21 days apart. Hemagglutination inhibition (HAI) and microneutralization (MN) antibodies were measured on days 0, 10, 21, 31, 42, and 201. Results. Recipients of 30 μg HA had significantly higher HAI geometric mean titers (GMTs), compared with recipients of 15 μg HA on days 10 (139.0 vs 51.9; P 5 .01), 21 (106.7 vs 51.9; P = .001), and 31 (130.0 vs 73.7; P = .03) but not on days 42 (91.8 vs 61.6; P = .11) and 201 (43.0 vs 27.0; P = .08). When analyzed by CD4 cell count stratum, HAI GMTs were significantly higher among 30 μg HA recipients than among 15 μg HA in the CD4 cell count, 200 cells/mL stratum on days 21 and 31 and the MN GMTs on days 10, 21, 31, and 42 (P < .05). In the CD4 cell count <200 cells/mL stratum, MN GMTs were significantly higher among recipients of 30 μg HA than among recipients of 15 μg HA on day 10 (P = .03). Conclusion. Increasing the HA dose of the 2009 H1N1 vaccine improves the vaccine's immunogenicity in HIV-infected individuals. [ABSTRACT FROM AUTHOR]