Changes in Antibody Avidity after pH1N1 Vaccination by Age Group and Baseline HAI.

<p>Data were derived from HIV-infected children and youth who received 2 doses of pH1N1 monovalent vaccine (30 μg/dose) approximately 3 weeks apart. Data represent medians and Inter Quartile Range (IQR) of the avidity index (AI). The number of subjects per group at each time point is listed on the graph. <b>A</b> presents the AI responses for all subjects and also for the subjects divided by baseline pH1N1 HAI immune serostatus (HAI titer <1:40 versus ≥1:40). Overall, AI significantly increased post-dose 2 (p = 0.04) and remained slightly higher at 7 mo (p = 0.07). Only subjects seroprotected at baseline had significant AI increases after vaccination (p<0.0001, <0.0001 and 0.003 post-dose 1, post-dose 2 and 7 months post-dose 1, respectively). Baseline seropositive participants with HAI titers ≥ 1:40 had a significantly higher AI response to vaccination compared with participants with baseline HAI titers <1:40 (p = 0.02 at both post-dose 1 and post-dose 2). <b>B</b> shows AI responses in each age group. In the 4 to <9-year old group, there were no significant differences in AI between baseline and any subsequent time point. In the 9 to <18-year old group, there were significant AI increases at post-dose 2 and at 7 months (p = 0.04 and 0.048 respectively). In the 18 to <25-years old group, there were significant differences from baseline at all time points (p = 0.02, 0.04 and 0.002, respectively).