This study will have four assessment waves: Baseline, T2 follow up (6 months), T3 follow up (12 months), and T4 follow up (24 months). Physical health data and biological samples will be collected by research nurses and research assistants during health assessment session held in community centers. Questionnaire data will be collected by trained interviewers during telephone survey. To minimize attrition, a package of questionnaires and a sheet of instructions and equipment (i.e. brushes) for swab-taking at home may also be sent to parents upon request.