Inclusion Criteria:  Participated in one of the parent studies Confirmed HIV-1 infection based on documented nucleic acid testing of two blood samples collected at different time points Received early treatment for HIV-1 infection, defined as treatment with at least three ARV agents from at least two classes of ART, initiated within 12 weeks of birth Based on parent or guardian report at entry, child is expected to be available for at least 24 months of follow-up Parent or guardian is willing and able to provide written informed consent for child's study participation and, when applicable per institutional review board/ethics committee (IRB/EC) policies and procedures, child is willing and able to provide written assent for study participation  Exclusion Criteria:  Has any documented or suspected clinically significant medical condition or any other condition that, in the opinion of the site investigator, would make participation in the study unsafe or otherwise interfere with completing study procedures