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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

A novel swine-origin influenza A subtype H1N1 virus, designated 2009 H1N1 influenza A, was identified as the cause of pandemic febrile respiratory illnesses [1–4]. Although individuals of all ages were affected, the greatest increase in severe morbidity and mortality occurred in young children, pregnant women, and the morbidly obese [5]. In human immunodeficiency virus type 1 (HIV-1)–infected patients, influenza infection is more severe than that typical of age-matched uninfected people [6, 7]. HIV-1–nfected patients also may shed virus for greater periods of time, prolonging the need for isolation in the clinic or hospital [8]. Because of the increased severity of this pandemic in children and young adults, knowledge of the safety and immunogenicity of the pandemic influenza A (pH1N1) 2009 monovalent vaccine in this population is critically important. Antibody responses to seasonal trivalent influenza vaccine (TIV) are blunted in HIV-1–infected children and adults who are not receiving antiretroviral therapy (ART) [9–11] but improved in patients who do not have progressive HIV-1 disease and/or are receiving combination ART (cART) [12–16]. Still, the immunological response is poorer compared to that of HIV-uninfected cohorts [15, 16]. Studies evaluating the effect of antigen dosage on the immune responses to TIV performed over the past 35 years demonstrate dose-related increases in serum and mucosal antibody responses [17–25]. Higher vaccine dosages are also associated with the development of higher levels of serum antibodies that recognize antigenically distinct drift variants [23] and can overcome suboptimal responses in immunologically impaired vaccinees, such as elderly patients [22, 24, 25]. However, higher dosages of hemagglutinin are also associated with more frequent adverse events. We hypothesized that 2 doses of influenza vaccine would be necessary to achieve protection in perinatally HIV-1–infected children and youth who had no prior exposure to pH1N1. In addition, because of blunted response to TIV in HIV-1–infected persons, we investigated a 30-μg dose of antigen, double the 15-μg dose proposed for healthy children.

Background Peripheral blood lymphocyte subsets need to be determined in a large, urban, minority-predominant cohort of healthy children to serve as suitable control subjects for the interpretation of the appearance of these cells in several disease conditions, notably pediatric HIV-1 infection. Objective We sought to determine the distribution of lymphocyte subsets in healthy urban-dwelling infants, children, and adolescents in the United States. Methods Lymphocyte subsets were determined by means of 3-color flow cytometry in a cross-sectional study of 807 HIV-unexposed children from birth through 18 years of age. Results Cell-surface marker analysis demonstrated that age was an extremely important variable in 24 lymphocyte subset distributions measured as percentages or absolute counts—eg, the CD4 (helper) T cell, CD8 (cytotoxic) T cell, CD19 B cell, CD4CD45RACD62L (naive helper) T cell, CD3CD4CD45RO (memory helper) T cell, CD8HLA-DRCD38 (activated cytotoxic) T cell, and CD8CD28 (activation primed cytotoxic) T cell. The testing laboratory proved to be an important variable, indicating the need for using the same laboratory or group of laboratories to assay an individual's blood over time and to assay control and ill or treated populations. Sex and race-ethnicity were much less important. Conclusion The results of this study provide a control population for assessment of the effects of HIV infection on the normal development and distribution of lymphocyte subsets in children of both sexes, all races, and all ethnic backgrounds from birth through 18 years of age in an urban population. This study's findings will also prove invaluable in interpreting the immune changes in children with many other chronic diseases, such as primary immunodeficiency, malignancy, rheumatoid arthritis, and asthma.