TUESDAY, Nov. 9 (HealthDay News) -- Few teenage girls and young women are getting the human papillomavirus vaccine (HPV), and many of those who start the regimen fail to take all three doses, new research reveals.

Although studies have shown that the HPV vaccine is safe and effective against several strains of the sexually transmitted virus, just one-third of teens and young women who start the three-dose series actually finish, and almost three-quarters don't start it at all, according to research being presented this week at the American Association of Cancer Research annual meeting in Philadelphia.

"Women who are eligible for this vaccine and could potentially benefit aren't getting it at rates to maximally prevent cervical cancer," said study author J. Kathleen Tracy, an assistant professor of epidemiology and public health at the University of Maryland School of Medicine in Baltimore.

"This highlights the need for public health promotions and practice patterns to encourage vaccine uptake or at least discussion of the pros and cons," Tracy said.

Tracy has initiated a study to see if text messages will prompt women aged 18 to 26 to keep their follow-up appointments for subsequent doses of the vaccine.

According to background information in the abstract, about 30 percent of sexually active 14- to 19-year-olds are infected with HPV at any one time. Over time, persistent infection can lead to cervical cancer.

Two HPV vaccines are marketed in the United States. Gardasil, approved in 2006 for girls aged 9 and up, protects against four types of HPV, two of which cause about 70 percent of cervical cancers worldwide.

Cervarix, which covers the two strains of the virus responsible for most cases of cervical cancer, was approved in 2009.

The U.S. Centers for Disease Control and Prevention recommends that 11- and 12-year-old girls be targeted for the vaccine as most in this age group are not yet having sex and would therefore not have been exposed to HPV yet.

A 2008 survey, conducted before Cervarix was approved, found that only about half of American mothers intended to have daughters younger than 13 vaccinated against human papillomavirus (HPV), despite government guidelines suggesting the opposite.

These authors looked at medical records on 9,658 girls and women aged 9 through 26 who were seen at the University of Maryland Medical Center between August 2006 and August 2010.

Only 27.3 percent of them opted to start the vaccine.

And of these, 39.1 percent completed just one dose, 30.1 percent got two doses and 30.7 percent finished the series.

Blacks were less likely than white women to get all three doses, and women aged 18 through 26 were less likely than younger girls to complete the series.

Dr. Mark Wakabayashi, chief of gynecologic oncology at City of Hope Cancer Center in Duarte, Calif., thinks suspicions about vaccines in general, including a lingering concern that childhood vaccinations can cause autism, may cause some reluctance. Those fears about autism are generally considered to be unfounded.

The stigma surrounding sexually transmitted diseases may also be a deterrent. "There are these connotations with sexually transmitted diseases, so I think a lot of parents feel that, when you're talking about minors, everybody else should have the vaccine except their own child," said Wakabayashi, who recommends the vaccine to his patients.

Tracy speculated that women aged 18 to 26 may be caught up in life's transitions at that point, like leaving home and going to college. For many young women, this is the first time they are making their own medical decisions.

As for the younger age group, parents also get busy or may be less enthusiastic about a second dose if there was a side effect, such as pain at the injection site or fainting, after the first shot, she speculated.

Recent research from the University of Minnesota School of Public Health, which was published in the journal Health Affairs, also found that ongoing news reports regarding mandatory vaccination of middle-school students diminished support for the policy.

More information

The U.S. Centers for Disease Control and Prevention has more on HPV and on HPV vaccines.