Serum samples will be obtained from all participants on day 1, at month 3, and at month 7. Samples will be de-identified and stored at -20°C or below and anti-HPV levels will be determined using an HPV type-specific competitive Luminex xMAP-based immunoassay (cLIA). (18) Merck will make arrangements for the labs tests. This assay measures only neutralizing anti-HPV antibodies, rather than the broad assortment of vaccine-induced anti-HPV antibodies. Antibody levels will be expressed as milliMerck units (mMU) per milliliter. The lower limits of detection for the anti-HPV 6, 11, 16, and 18 cLIAs are 4.1 mMU6/mL, 3.0 mMU11/mL, 10.2 mMU16/mL, and 2.9 mMU18/mL, respectively. Assay precision is estimated to be 21.7%, 20.4%, 23.0%, and 15.9% for the anti-HPV 6, 11, 16, and 18 cLIAs respectively. Participants will be considered anti-HPV 6, 11, 16, or 18 seropositive when their anti-HPV antibody titers are 20 mMU6/mL, 16 mMU11/mL, 20 mMU16/mL, or 24 mMU18/mL, respectively.