Mother inclusion criteria: - Be on standard of care (SOC) antiretroviral therapy for human immunodeficiency virus type 1 (HIV-1) treatment. - Have confirmed HIV-1 infection based on positive test results obtained from medical records. Neonate inclusion criteria: - Be born at term (≥ 37.0 weeks gestational age). - Be able to take oral medication. - Be ≤ 120 hours of life at enrollment. - Have a birth weight ≥ 2.5 kg. - Is receiving or plans to receive HIV-1 SOC prophylaxis regimen with 1 antiretroviral (ARV) to prevent perinatal transmission.

Mother exclusion criteria: - Has a maternal-fetal blood group incompatibility identified by clinically relevant antibody that can cause hemolytic diseases of the neonate. - Is breastfeeding or plans to breastfeed while on bictegravir (BIC) or emtricitabine (FTC) containing regimen. Mothers on BIC or FTC containing regimen, but not breastfeeding, can be enrolled in the study. Neonate exclusion criteria: - Had prior or expected to require blood exchange transfusion. - Is receiving or plans to receive any component of B/F/TAF or dolutegravir as part of their SOC ARV prophylaxis regimen. - Has a documented positive HIV-1 nucleic acid test. - Has Grade 2 or higher aspartate aminotransferase, total bilirubin, hemoglobin, platelets or creatinine. Has Grade 1 or higher alanine aminotransferase. Note: Other protocol defined Inclusion/Exclusion criteria may apply.