a A positive response was defined as any response ≥ 20 pg/ml above that of unstimulated cell culture supernatants and had a positive or negative blood smear. b Geometric mean cytokine levels in pg/ml. c NS= not significant. P < 0.05 considered significant, as determined by χ2 test for trend across age groups. dP < 0.05 was considered significant as determined by analysis of variance of log-transformed values across age groups.