Prevention of Mother-to-child Transmission of HIV-1 Using a Responsive Intervention

In the intervention arm, HIV-1 negative children with HIV-1 positive mothers who have an HIV-1 viral load ≥ 1000 copies/ml will receive lamivudine syrup orally (7.5 mg twice daily if 2 to 4 kg; 25 mg twice a day if weight \<8 kg; and 50 mg twice a day if weight \>8 kg). The intervention will last a maximum of 10 months (until the baby is 12 months old or until the confirmed end of breastfeeding). Breastfeeding will be considered to be ceased if the mother confirms she is no longer breastfeeding for 2 consecutive monthly visits