Condition: Human Immunodeficiency Virus Infection

This is a single-group, open-label, multi-site study in pediatric participants with human immunodeficiency virus type 1 (HIV-1) infection, aged 4 weeks to <12 years and weighing <45 kg, who are treatment-naive (TN) or have been virologically suppressed (VS) on stable combination antiretroviral therapy (cART) for ≥3 months with no history of treatment failure. The first primary objective is to evaluate the steady state pharmacokinetics (PK) of doravirine (DOR) [MK-1439] when given in combination with 2 nucleoside/nucleotide analog reverse transcriptase inhibitors (NRTIs) or as part of the fixed dose combination (FDC) of DOR/lamivudine (3TC)/tenofovir disproxil fumarate (TDF) in participants ≥6 to <12 years and weighing ≥14 to <45 kg. The second primary objective is to evaluate the safety and tolerability of DOR when given with 2 NRTIs or as part of the FDC of DOR/3TC/TDF, in participants ≥6 to 12 years and weighing ≥14 to <45 kg, through Week 24.