Girls who thought this were less likely to have information about the vaccine and about HPV infection.
Doctors who discuss the HPV vaccine with girls and their parents ''may need to emphasize the limitations of the vaccine and to specifically address that the vaccine does not prevent other STIs,'' the researchers wrote.
Mullins said it is not known how girls perceive risk after the entire three-dose series.
The study was supported by the U.S. National Institutes of Health.
Some study co-authors reported receiving grants from Merck, which makes Gardasil. One reported doing consulting work for Sanofi Pasteur, which has marketed Gardasil in Europe.
The study results bear "no big surprises," said Dr. H. Hunter Handsfield, a member of the board of directors for the American Social Health Association and a professor of medicine at the University of Washington Center for AIDS and STD in Seattle. He is an advisor to Merck for its HPV vaccine.
"If anything, it's a fairly pleasing result that it's only 24 percent [who think the HPV vaccine protects against other STIs]," he said.
Before the vaccines were available, Handsfield said, "social and religious conservatives" expressed worries that teens would practice safe sex less often after getting the vaccine. The latest findings suggest this isn't happening by and large, he noted.
Doctors do need to be clear with their young patients when giving them the HPV vaccine, Handsfield said. They need to tell them that the vaccine does not protect against all STIs, and that when the patients become sexually active they need to practice safer sex behaviors, such as using condoms.
For more on HPV, go to the U.S. National Library of Medicine.
SOURCES: Tanya Kow
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