Inclusion Criteria:
1. Males and females 15-26 years old.
2. Ability to give informed consent. All participants under 18 years of age must have the informed consent of a parent and must assent to participation.
3. Has not received any prior doses of the HPV vaccine. Investigators will ask the patient and his/her parent (if \<18) about prior vaccination and check the state registry (Immtrac), as well as the UTMB electronic medical record (if previously seen at UTMB), investigators will check with their primary care provider, if feasible, for patients who are not a previously established UTMB patient.
4. Identified source of funding for vaccine which may include Texas Vaccines for Children (VFC) program, Medicaid, the Children's Health Insurance Plan (CHIP), Texas Healthy Women program or other public or private health insurance.
5. Reliable telephone access.
6. Participant and parent/ guardian (if \<18) can read and speak either English or Spanish.
Exclusion Criteria:
1. For females, currently pregnant or plans to become pregnant or donate eggs in next 12 months. Sexually active females must report that they use regular birth control. All female subjects will be required to take a urine pregnancy test before each Gardasil 9 dose, unless it can be verified that she gave birth within the last week. Any subjects with positive tests at the initial visit will be disqualified from the study and advised to seek prenatal care. If a subject is pregnant when her follow-up visit window closes, she will be removed from the study.
2. History of 6 or more lifetime sexual partners.
3. History of any immunodeficiencies (HIV+, chemotherapy treatment, status splenectomy) or autoimmune disorders (lupus, thyroid disorder, psoriasis).
4. History of bleeding or platelet disorders such as hemophilia.
5. Currently taking medication which can suppress immune function including systemic corticosteroids, radiation therapy, cyclophosphamide, azathioprine, methotrexate, cyclosporine, leflunomide, TNF-alpha antagonists, monoclonal antibody therapies, or intravenous immunoglobulin treatment.
6. Known allergies to any components of the vaccine, including aluminum, yeast or Benzonase.
7. Febrile at ≥100°F in the 24 hours prior to vaccination. This will be reviewed before each Gardasil 9 dose.
8. Received any non-study inactive vaccines within the past 14 days or any live vaccines within the past 30 days. Those excluded for this reason will be re-screened under the same study number at a later date.
9. Plan to move out of the Galveston/Houston area in the 13 months following study entry.
