Immunogenicity of Licensed Influenza A (H1N1) 2009 Monovalent Vaccines in HIV-Infected Children and Youth

Abstract

Background: With the emergence of pandemic influenza A (pH1N1) in 2009, children and youth infected with human immunodeficiency virus (HIV) were vulnerable because of immunologic impairment and the greater virulence of this infection in young persons.

Methods: A multicenter study of the immunogenicity of 3 licensed influenza A (H1N1) monovalent vaccines (1 live attenuated and 2 inactivated) was conducted in children and youth with perinatal HIV infection, most of whom were receiving ≥3 antiretroviral drugs, had CD4% ≥15, and plasma HIV RNA levels <400 copies/mL. Serum hemagglutinin inhibition assay (HAI) antibody levels were measured and correlated with baseline demographic and clinical variables.

Results: One hundred forty-nine subjects were enrolled at 26 sites in the United States and Puerto Rico. Over 40% had baseline HAI titers ≥40. For subjects aged 6 months to <10 years, 79% and 68%, respectively, achieved a ≥40- and ≥4-fold rise in HAI titers after the second dose of vaccine. Three weeks after a single immunization with an inactivated vaccine, similar immunogenicity results were achieved in youth aged 10-24 years. With multivariable analysis, only Hispanic ethnicity and CD4% ≥15 were associated with achieving both HAI titer ≥40- and ≥4-fold rise in titer.

Conclusions: Although licensed pH1N1 vaccines produced HAI titers that were considered to be protective in the majority of HIV-infected children and youth, the proportion with titers ≥40- and ≥4-fold rise in titer was lower than expected for children without HIV infection. Vaccine immunogenicity was lower in HIV-infected children and youth with evidence of immune suppression.

Figure 1.

Enrollment and follow-up of subjects. Subjects were disqualified and nonevaluable if they failed to meet inclusion criteria or developed an exclusion criterion. A, In Group A, the sole subject aged <10 years and 3 of the ≥10 year subjects were excluded because of a dosing error. One subject was excluded because of prior receipt of 2009 Influenza A (H1N1) vaccine. B, In Group C, 1 subject aged <10 years was excluded because of flu at study entry. C, In Group C, 1 subject aged ≥10 years was disqualified because of prednisone treatment and another had flu at study entry. D, In Group B, 1 subject aged ≥10 years was disqualified because of a flu-like illness. E, In Group C, another subject aged ≥10 years was disqualified because of a flu-like illness. Abbreviations: DQ, disqualified; ILI, influenza-like illness.