Comparisons between the two groups in terms of the ELISA and SBA results were performed by Student’s t-test or the Mann–Whitney click here test. Mean

pre- and post-vaccination titers (ELISA and SBA) were compared by paired Student’s t-test or the Wilcoxon test. Intragroup differences between pre- and post-vaccination values were considered statistically significant at a level of 5%. In addition, a difference between two groups of similar size and similar variance whose 95% CIs do not overlap was considered significant at a level of approximately 5%, thus enabling significant differences between groups to be assessed by non-overlapping CIs. Chi-square tests (χ2) or Fisher’s exact tests were used to compare the groups in terms of the proportions find more of patients with SBA titers ≥8, patients

showing a 4-fold rise in SBA titers, patients who responded to the vaccine, and patients who experienced side effects. The remaining variables of the study, including sociodemographic and clinical variables, were analyzed by descriptive statistics – mean (standard deviation) or median (minimum and maximum) – when quantitative and by proportions when qualitative. A level of significance of 5% was considered for all statistical tests. The statistical software used in all analysis was the Statistical Package for the Social Sciences, version 14.0 (SPSS Inc., Chicago, IL, USA). We included a total of 92 individuals in the study (mean age = 13.9 years, range 10–19 years), from May to December 2009: 43 in the HIV+ group (mean age = 13.8 years; range 10–19 years); and 49 in the HIV− group (mean age = 13.9 years; range 10–19 years). In the sample as a whole and in each

of the two groups, 52.7% of the patients were female and 47.3% were male. All of the patients in the HIV+ group were under treatment with highly active antiretroviral therapy (HAART). There were no losses in either of the study groups. As shown in Table 1, the mean level of post-vaccination Rolziracetam response was higher in the HIV− group than in the HIV+ group, whether evaluated by ELISA (p = 0.001) or by SBA (p < 0.001). The differences between groups are evidenced by the non-overlapping 95% CIs. Before vaccination, the percentage of patients with SBA titers ≥8 was higher in the HIV− group than in the HIV+ group (34.7% vs. 16.3%). There were significant differences between the two groups in terms of these titers (Table 1). In the HIV+ group, 35 (81.4%) of the patients had a post-vaccination SBA titer ≥8, compared with 100% of those in the HIV− group. A 4-fold increase in the SBA titer after vaccination was observed in 31 (72.1%) of the HIV+ group patients, again compared with 100% of those in the HIV− group (Table 1). We defined a positive antibody response to the vaccine as the combination of the established protective criteria (a post-vaccination SBA titer ≥8 and a 4-fold increase over the initial titer). Of the 43 HIV+ group patients, 31 (72.