Convenience sampling will be used to enroll a cohort of 600 HIV-uninfected infants between the ages of 4-5 months of age according to the following strata based on the mother's HIV status: 1) 200 HIV-exposed infants born to HIV-infected mothers, and 2) 400 HIV-unexposed infants born to HIV-uninfected mothers. Potential study participants will be identified from the Tororo District Hospital Antenatal Clinic and surrounding clinics providing routine pediatric care. Potential study participants less than 6 months of age and their parents/guardians will be referred to our study clinic for screening. Eligible children will be enrolled when they reach 4-5 months of age and followed until the age of 36 months for all their routine medical care at our designated study clinic. All mother-child pairs will receive 2 long lasting ITNs at enrollment and, as available, a basic care package including a safe water vessel, multivitamins and condoms. HIV-unexposed children will be randomized to one of four chemoprevention arms when they reach 6 months of age. All HIV-exposed children born to HIV-infected mothers will be given TS prophylaxis and mothers will be encouraged to introduce food at 6 months of life and continue breastfeeding until 1 year of life, in accordance with Ugandan Ministry of Health (MOH) guidelines. HIV-exposed children will retested for HIV approximately every 60 days during breastfeeding and 6 weeks following cessation of breastfeeding. HIV-exposed children who remain HIV-uninfected following cessation of breastfeeding will be randomized to one of four chemoprevention arms. HIV-exposed children who test positive for HIV during the course of the study (those who seroconvert during breastfeeding) will be excluded from the study and referred for appropriate care.