KANSAS CITY, Mo. -- Only about a third of girls who get the HPV vaccine get all three recommended doses on time.
The vaccine protects against a virus that causes cervical cancer.
Now a study in the Journal of the American Medical Association finds two doses may work for girls. Canadian researchers found two doses of Gardasil provided as much of an immune response for girls ages 9 to 13 as three doses given to young women. That was up to two to three years later. The findings suggest girls might be able to put off the hassle and expense of getting the third dose of Gardasil until they're older.
But a researcher of the vaccine at the UMKC School of Medicine says the study used manufacturer Merck's low threshold for protection -- not what independent scientists use.
"Girls that only got two doses of Gardasil did not make enough antibodies. They didn't get enough fighting cells going to be abel to take care of either genital warts or cervical cancer for the long-term protection," says Dr. Diane Harper.
Dr. Harper says if you know you're only going to get two doses, go with the other HPV vaccine called Cervarix.
She says a previous study showed Cervarix not only produced an immune response with two doses but actually prevented HPV infections which can result in cervical cancer.
But Cervarix does not protect against genital warts. So if you want protection against both, Dr. Harper says use Gardasil and be aware.
"You need to get all three doses and you need to get them on time."
That means a second dose one to two months after the first, and a third dose six months after the first.
The vaccine costs about $130 a dose.
Dr. Harper says women need a pap test beginning at age 21 even if they have received HPV vaccine.