ABTs below the detection limit of 1 1:10 were assigned a value of 1 1:5. Evaluation of vaccine safety. for PV were high during the first 6 months and declined below seroprotection levels thereafter. Longitudinal changes in ABTs were similar in groups 1 and 2 for both PV and SV. The side effects of vaccination were mild and mostly local. Ciprofloxacin hydrochloride hydrate In HIV-infected children, adolescents, and young adults, the immune response triggered by a single dose of PV was similar to that obtained with a double dose and was associated with long-term antibody response. INTRODUCTION In April 2009, a novel H1N1 influenza A virus was isolated in Mexico and in the United States, and its rapid worldwide diffusion led the World Health Organization to declare a new influenza pandemic within just 2 months (8). The rate of 2009 A/H1N1 infection was four times greater in children than in adults, and immunosuppressed individuals had a more severe course of the disease (8, 15). In September 2009, the Italian Ministry of Health recommended vaccination against 2009 A/H1N1 to all HIV-infected patients. In the meantime, the European Medicines Agency (EMA) issued a marketing authorization for two vaccines against 2009 A/H1N1 and allowed their administration together with the seasonal influenza vaccine. Two phase-2 randomized controlled trials have shown that a single dose of Rabbit Polyclonal to OR51G2 2009 pandemic A/H1N1 influenza vaccine is sufficiently immunogenic except for children younger than 9 years (18). Protection against influenza is provided mainly by antibody-mediated immunity, and HIV infection is associated with a decline in the number and function of antigen-specific memory B-cells that might hamper the response to vaccination (17). Owing to the novelty of the 2009 2009 A/H1N1 infection and the uncertain response of HIV-infected children Ciprofloxacin hydrochloride hydrate to vaccination, it was hypothesized that special vaccination schedules might be necessary in this population (21). We performed a randomized controlled trial (RCT) to assess the safety and long-term immunogenicity of one versus two doses of the monovalent 2009 A/H1N1 pandemic influenza MF59-adjuvanted vaccine coadministered with the seasonal 2009-2010 trivalent nonadjuvanted influenza vaccine to HIV-infected children, adolescents, and young adults. MATERIALS AND METHODS Study design. An RCT was performed between 15 October 2009 and 30 November 2010 to assess the long-term immunogenicity of the monovalent 2009 A/H1N1 pandemic influenza MF59-adjuvanted vaccine coadministered with the seasonal 2009-2010 nonadjuvanted influenza vaccine. Vertically HIV-infected children and adolescents followed as outpatients at the pediatric clinic of the L. Sacco Hospital (Milan, Italy) were studied. Eligible patients were aged 9 to 26 years and had received a seasonal influenza vaccine in the previous influenza season. Exclusion criteria were (i) body temperature 38C at the time of vaccination, (ii) ongoing or recent immunosuppressive treatment, (iii) blood transfusions or use of intravenous immunoglobulins during the previous month, and (iv) influenza-like illness during the previous month. Sixty-six consecutive HIV-infected patients were randomly assigned to receive one (group 1) or two (group 2) doses of the monovalent 2009 A/H1N1 pandemic influenza MF59-adjuvanted vaccine coadministered with a dose of the Ciprofloxacin hydrochloride hydrate seasonal 2009-2010 nonadjuvanted influenza vaccine. A second dose of the pandemic vaccine was administered only to group 2 within 28 5 days from the first dose. A computer-generated randomization list assigned participants in equal numbers to group 1 (= 33) or group 2 (= 33). A statistician who did not perform the final analysis generated the allocation sequence and assigned participants to the treatment groups. The study was approved by the Ethical Committee of the L. Sacco Hospital (Milano, Italy), and written informed consent was Ciprofloxacin hydrochloride hydrate obtained from the parents or legal guardians of the children and from the patients themselves. Assessment of immunological and virological status. CD4 cell counts and HIV RNA levels were measured at baseline and at 2 (56 5 days), 6 (168 10 days), and 12 (336 5 days) months after enrollment. CD4 cells were measured by flow cytometry using fresh blood samples and a Cytotron Absolute flow cytometer (Ortho Cytometry, Raritan, NJ) with Immunocount II software. HIV RNA was measured with a lower detection limit of 50 copies/ml (Quantiplex assay.