Children with light, moderate, and heavy infections had baseline IFN-γ levels of 107 ± 76, 74 ± 55, and 88 ± 76 pg/mL, respectively (mean ± SE for 71, 50, and 46 children, respectively), with no significant differences related to intensity of S. mansoni infection or occurrence of other parasites. This evidence concerns the gene IFNG and infection.