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Single HPV Dose Provides About 97% Protection Against Cancer‑Causing Virus, Large Trial Finds

A large randomized trial in Costa Rica led by the U.S. National Cancer Institute followed over 20,000 girls aged 12–16 for five years and found one HPV vaccine dose provided about 97% protection against cancer-associated HPV strains, comparable to two doses. Results published in the New England Journal of Medicine suggest a single-dose schedule could help expand vaccination in low-resource settings. Authors stress the need for longer follow-up and that the trial measured infection, not cancer outcomes.

09:52 AM, 12/04/2025Health
Single HPV Dose Provides About 97% Protection Against Cancer‑Causing Virus, Large Trial Finds

A major clinical trial led by the U.S. National Cancer Institute and Costa Rica’s Agency for Biomedical Research found that a single dose of the human papillomavirus (HPV) vaccine produced protection against the cancer-causing strains of HPV that was comparable to two doses over at least five years.

Key findings

The trial enrolled more than 20,000 girls aged 12–16 and tested two different HPV vaccine formulations used worldwide. Participants were assigned one vaccine type; six months later, half received a second dose of the same vaccine while the other half received an unrelated childhood vaccine. All participants were followed for five years with regular cervical screening focused on the HPV strains most strongly linked to cancer.

Researchers reported that one vaccine dose provided roughly 97% protection against infection with the most dangerous HPV strains — a level similar to that seen with two doses. The results were published in the New England Journal of Medicine.

“We have the evidence and tools to eliminate cervical cancer. What remains is the collective will to implement them equitably, effectively, and now,”

wrote Dr. Ruanne Barnabas, an infectious-disease specialist at Massachusetts General Hospital, in an accompanying editorial. She noted that earlier studies had suggested a single dose could be effective; this large randomized trial confirms strong protection through at least five years.

Implications and limitations

In many high-income settings, public health authorities recommend two HPV doses beginning at age 11 or 12, with catch-up vaccination advised through age 26 for those not previously immunized. The U.S. Centers for Disease Control and Prevention reports that about 78% of adolescents ages 13–17 have received at least one dose.

Globally, however, uptake is much lower: the World Health Organization estimates fewer than one in three adolescent girls have been vaccinated against HPV. If a single-dose schedule is confirmed to provide long-term protection, it could simplify immunization programs and help expand coverage in low-resource settings where completing multi-dose schedules is difficult.

Study authors caution that the trial measured protection against persistent infection with cancer-associated HPV strains, not cancer outcomes directly. The trial did not provide data on HPV-related cancers outside the cervix (such as head and neck cancers), and longer-term follow-up is needed to confirm sustained protection and to measure any impact on actual cancer rates.

Overall, the findings strengthen evidence that a single HPV dose can provide substantial short- to mid-term protection and could be a valuable tool for broadening global vaccine access.

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