A single shot of HPV vaccine may be enough to fight cervical cancer,
study finds
[December 04, 2025]
By LAURAN NEERGAARD
WASHINGTON (AP) — A single HPV vaccination appears just as effective as
two doses at preventing the viral infection that causes cervical cancer,
researchers reported Wednesday.
HPV, or human papillomavirus, is very common and spread through sex.
Most HPV infections clear up on their own but some linger, causing
cancers that appear years later, including cervical cancer in women and
rarer cancers in both women and men.
HPV vaccination has been recommended for U.S. girls since 2006 and
already the nation is counting fewer cases of precancerous cervical
lesions among women in their 20s —- the first age group to start getting
the shots back when they were tweens or teens.
But cervical cancer kills about 340,000 women worldwide annually — and
the new findings from a huge study in Costa Rica could help spur global
efforts to protect more girls and young women in harder-to-reach
low-income countries.
Led by the U.S. National Cancer Institute, the study enrolled more than
20,000 girls between ages 12 and 16. Researchers tested two different
HPV vaccines used around the world, giving half the girls one shot type
and the rest the other. Then six months later, half of the girls got a
second dose of their assigned vaccine — while the rest instead received
an unrelated child vaccination.
They all were tracked for five years, receiving regular cervical tests
for the most cancer-prone HPV strains. Infection rates were compared to
a separate unvaccinated group.
A single HPV shot provided about 97% protection, similar to two doses,
concluded researchers from the NCI and Costa Rica’s Agency for
Biomedical Research. The findings were reported in the New England
Journal of Medicine.
Previous studies had suggested one dose could work well but the new
findings confirm strong protection for at least five years, Dr. Ruanne
Barnabas, an infectious disease specialist at Massachusetts General
Hospital, wrote in an accompanying editorial.
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A doctor holds a vial of the human papillomavirus (HPV) vaccine
Gardasil in Chicago on Aug. 28, 2006. (AP Photo/Charles Rex Arbogast,
File)
 “We have the evidence and tools to
eliminate cervical cancer. What remains is the collective will to
implement them equitably, effectively, and now,” wrote Barnabas, who
wasn’t involved in the Costa Rican study.
The U.S. recommends two HPV shots starting at age 11 or 12 for most
girls and boys — as the virus also can cause head-and-neck and other
cancers. Catch-up shots are recommended for anyone through age 26
who hasn't been vaccinated. The Centers for Disease Control and
Prevention has reported about 78% of 13- to 17-year-olds have gotten
at least one dose.
But globally, the World Health Organization estimates less than a
third of adolescent girls have been vaccinated — and the agency
already had begun recommending either one or two doses in an effort
to broaden protection.
The new study offered no information about HPV-related cancers
beyond the cervix, and the researchers cautioned that longer
monitoring is needed.
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