IFNG and diphtheria: Our results show that: i) congenitally T. cruzi-infected newborns (M+B+) display an early ability to produce the type 1 cytokine IFN-γ; ii) their specific responses (M+B+) to the hepatitis B vaccine, and to a lesser extend to diphtheria and tetanus vaccines, administered later after birth are characterized by higher levels of IFN-γ and/or protective IgG antibodies; and iii) non-infected infants born to T. cruzi–infected mothers (M+B−) secrete higher amounts of IFN-γ in response to BCG vaccination administered at birth.