Doravirine (DOR) in Human Immunodeficiency Virus (HIV)-Infected Children Aged 4 Weeks to <12 Years and <45 kg (MK-1439-066)

Inclusion Criteria: * Has human immunodeficiency virus type 1 (HIV-1) infection confirmed at screening * Has appropriate treatment history defined as treatment-naïve (TN) or with documented virologic suppression (HIV-1 ribonucleic acid \[RNA\] \<50 copies/mL) on stable combination antiretroviral therapy (cART) for ≥3 months * Body weight is \>3 kg to \<45 kg * If female, is not pregnant or breastfeeding, and one of the following applies: * Is not a woman of childbearing potential (WOCBP) * Is a WOCBP using an acceptable form of contraception, or is abstinent * If a WOCBP must have a negative pregnancy test (urine or serum) within 24 hours of the first dose of study intervention Study Extension Inclusion Criteria: * Has completed the Week 96 visit * Is considered, in the opinion of the investigator, to have derived benefit from treatment with doravirine (DOR) plus the 2 nucleoside/nucleotide analog reverse transcriptase inhibitor (NRTIs) selected by the investigator, or doravirine/lamivudine/tenofovir disoproxil fumarate (DOR/3TC/TDF), by Week 96 of the study * Is considered, in the opinion of the investigator, to be a clinically appropriate candidate for additional treatment with DOR regimens (DOR plus 2 NRTIs selected by the investigator or DOR/3TC/TDF) * Understands the procedures in the study extension and has provided (or have the participant's legally acceptable representative, if applicable, provide) documented informed consent/assent to enter the study extension and…