Background: Early antiretroviral treatment (ART) improves outcomes in children, but few studies have comprehensively evaluated the impact of ART started from the first week of life.

Methods: Children diagnosed with HIV within 96 hours of life were enrolled into the Early Infant Treatment Study in Botswana and followed on ART for 96 weeks. Nevirapine, zidovudine, and lamivudine were initiated; nevirapine was switched to lopinavir/ritonavir between weeks 2-5 in accordance with gestational age. Clinical and laboratory evaluations occurred at weeks 1, 2, 4, 8, 12, 24, 36, 48, 60, 72, 84, and 96.

Findings: Forty children initiated ART at a median of 2 (IQR 2, 3) days of life; 38 (95%) completed follow-up through 96 weeks, and 2 (5%) died between 12 and 24 weeks. ART was well tolerated; 9 children (24%) experienced a grade 3 or 4 hematologic event, and 2 (5%) required treatment modification for anemia. The median 96-week CD4 count was 1625 (IQR 1179, 2493) cells/mm 3 with only 5/38 (13%) having absolute counts <1000 cells/mm 3 . Although 23 (61%) had at least one visit with HIV-1 RNA ≥40 copies/mL at or after 24 weeks, 28 (74%) had HIV-1 RNA <40 copies/mL at the 96-week visit. Median cell-associated HIV-1 DNA at 84/96-week PBMCs was 1.9 (IQR 1.0, 2.6) log 10 copies/10 6 cells. Pre-ART reservoir size at birth was predictive of the viral reservoir at 84/96 weeks.

Interpretation: Initiation of ART in the first week of life led to favorable clinical outcomes, preserved CD4 cell counts, and low viral reservoir through 96 weeks of life.