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 continue treatment with DOR regimens (DOR plus 2 NRTIs selected by the investigator or DOR/3TC/TDF) until it is available locally in countries participating in the study or for up to an additional 224 weeks (whichever comes first) Exclusion Criteria: * Has evidence of renal disease * Demonstrates evidence of liver disease * Has clinical or laboratory evidence of pancreatitis * Has any history of malignancy * Has presence of any active acquired immunodeficiency syndrome (AIDS)-defining opportunistic Infection * Has an active diagnosis of hepatitis, including hepatitis B co-infection * Has current active tuberculosis and/or is being treated with a rifampicin-containing regimen * Has a medical condition that precludes absorption or intake of oral pellets/granules * Has a history or current evidence of any condition, therapy, laboratory abnormality, or other circumstance that might confound results of the study or interfere with participating for the entire duration of the study * Is taking or is anticipated to require systemic immunosuppressive therapy, immune modulators, or other prohibited therapy * Is currently participating in or has participated in an interventional clinical study with an investigational compound or device from 45 days prior to Day 1 through the treatment period * Has a documented or known virologic resistance to DOR * Has any history of viremia (HIV RNA \>1000 copies/mL) after at least 3 months on a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen