In primates, immunization of pregnant baboons with a rhesus rotavirus vaccine increased milk immunoglobulin and virus neutralizing titre [45] . Prenatal immunization of pregnant women with a single dose of meningococcal vaccine not only increased antigen-specific IgG antibody in the infant's serum during the initial 2-3 months after birth, but antigen-specific IgA in milk continued to be elevated at least up to 6 months [46]. As discussed in section 4, IgG transfer to the offspring in humans occurs during late pregnancy and provides the initial systemic source of that immunoglobulin. Infants consuming breast milk will primarily be consuming secretory IgA (section 4), which has significant protective activity in the intestine, as discussed in section 5.2.