Study Procedures. Enrolled mothers will be asked to complete demographic and behavioural questionnaires, a participant locator form, and undergo phlebotomy and mechanical expression of breast-milk at the enrolment visit for determination of anti-rotavirus IgG and IgA (in serum and breast-milk). Infants will have a baseline anti-rotavirus IgA and IgG antibodies determined to ascertain baseline exposure to wild-type and transplacental immunoglobulin followed by a second serum IgA determination one month following completion of rotavirus vaccination (at approximately 14-20 weeks).