Could 2 HPV vaccine doses be enough? new study says maybe.
NCT ID NCT03943875
First seen Jun 24, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This study looked at whether 2 doses of the HPV vaccine (Gardasil 9) protect as well as the standard 3 doses in people aged 15 to 26. Researchers measured antibody levels against nine HPV types. The goal is to see if a simpler schedule could work, making vaccination easier and cheaper.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- 9-valent HPV vaccine (Gardasil 9)
- What this could lead to
- If 2 doses work as well as 3, it could simplify HPV vaccination schedules, reduce costs, and make it easier for more people to get protected against HPV-related cancers.
- What could go wrong
- This is a completed Phase 4 study, but it only measured short-term antibody responses, not long-term cancer prevention. Two doses may not provide the same lasting protection as three doses.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
-
Phase 4
Runs after approval, following long-term safety and how well the treatment works in everyday use.
- Participants
-
767 people
The number who actually took part.
- Started
-
Jun 2019
- Finished
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Jan 2025
- Lead sponsor
-
Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
-
15 to 26 years
- Sex
-
Anyone
- Healthy volunteers
-
Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
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.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
-
University of Texas Medical Branch
Galveston, Texas, 77555, United States
More trials for these conditions
Other studies related to the condition(s) this trial covers.
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- Can a new injection shrink advanced solid tumors?
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- Could a simple Self-Swab revolutionize cervical cancer screening?