Changes in CD4+T lymphocyte counts in vaccine recipients and non-recipients. Differences in CD4+ T cell counts between the nearest sampling time point before vaccination and a second time point within 1–5 months after vaccination are shown for the vaccine recipients. The groups labeled “Vaccinated I” include all individuals receiving the vaccine while those labeled “Vaccinated II” exclude individuals whose HIV virus load changed by > 1 log10 over the observation period. Changes in CD4+ T lymphocyte counts over an equivalent period are shown for the group of non-vaccinated individuals (a). Changes in CD4+ T cells for the same group (I) and subgroup (II) of vaccine recipients over a similar time interval approximately 1 year later are compared in panels b and c to changes in CD4+ T cells observed over the post H1N1 vaccine period. Lines within groups show the group median with IQR and the p value indicating probability of no significant difference between groups is shown above lines spanning the groups being compared.