- Subject's parent must provide voluntary written informed consent for subject to participate in the study, is fully capable of comprehending and complying with study requirements and procedures, able and willing to return for all scheduled follow-up visits, and has expressed availability for the required study period, with access to a consistent means of telephone contact. An illiterate parent will require an impartial witness to be present during consenting process to include discussing the consent form, verbal consent and thumb-printing.