Follow-up evaluations will be conducted at Weeks 2 and 6 and Months 3, 6, 12, and 18 for mothers, and at Weeks 2, 5, 6, and 8 and Months 3, 4, 5, 6, 9, 12, and 18 for infants. Study visits will include physical examinations, blood tests (including HIV tests), and medical histories. Study participants will be followed for up to 3.5 years.