Chrissy Thomas of Mililani is always looking for ways to protect her children. After hearing about the HPV (human papillomavirus) vaccine and doing some research, she decided to get the series of three doses for her daughters, Amanda, 17, and Carina, 15.

“With as many sexually transmitted diseases that there are out there, I felt that the HPV vaccine was well worth it to protect my daughters,” she said.

For other parents the decision to immunize their children against HPV, an infection that can cause genital warts and cancer, might not be so clear cut. Because public health recommendations call for immunizing girls, and even boys, in their preteen years before they are sexually active, the public health discussion of HPV vaccine has been clouded by political and social controversy. Some have even referred to it as “the sex vaccine.”

Health officials say some parents might mistakenly think their daughters don’t need the HPV vaccination at such a young age because they aren’t sexually active. Others might believe it would require a discussion with their children about sex and sexuality — a talk they might not be ready to have.

“Some parents might worry that it’s implicit acknowledgement of sexual activity among their teens and tweens. But nothing could be further from the truth. You want to protect your child as much as possible before they are sent off into the world,” said state epidemiologist Sarah Park of the state Department of Health.

Hawaii is doing better than most other states in terms of HPV immunization, with approximately 40 percent of adolescent girls in Hawaii ages 13 to 17 having completed the three-dose vaccine series, according to a recent report by the U.S. Centers for Disease Control and Prevention.

The state ranks 14th nationally in that regard, with Rhode Island at the top with 55 percent, according to the study, which was based on the 2010 National Immunization Survey-Teen, which relied on telephone surveys. The national figure is 32 percent.

Yet HPV vaccination lags other immunizations for middle school youths in Hawaii. The same study estimated that almost 79 percent of all adolescents had either the Td or Tdap booster immunizations for tetanus, diphtheria and pertussis, and almost 65 percent had received the vaccine to prevent meningitis.

HPV infection is the most common sexually transmitted infection in the United States. Most people who become infected with HPV do not even know they have it and do not develop health problems.

In 90 percent of cases, the body’s immune system clears the virus naturally within two years, the CDC says. But when HPV infections are not cleared, they can cause genital warts and cervical cancer and other, less common but serious cancers, including cancers of the vulva, vagina, penis and anus.

A report this month by Ohio State University and the National Cancer Institute researchers reported HPV is fueling a rise in cancers of the back of throat, including the base of tongue and tonsils, for which men are at greater risk.

About 12,000 women a year in the United States get cervical cancer, and almost all of these cases are HPV-related, the CDC said. Approximately 4,000 women die of this cancer each year, and several hundred thousand need surgery or treatment for precancerous lesions or other cervical abnormalities caused by HPV.

“It’s a new concept that an infection can lead to a chronic disease. The vaccine is a means of prevention early on for something that could happen years down the road,” Park said. “It’s a neat idea to be able to prevent a pretty bad cancer with a vaccine.”

Immunization is recommended for 11- and 12-year-old girls but can also be given to girls beginning at age 9. The second dose should be administered one to two months after the first dose, and the third dose six months after the first dose.

Although HPV vaccines are most effective when given before exposure to HPV through sexual contact, the CDC says girls and women 13 to 26 years of age who did not get any or all of the shots when they were younger should still get vaccinated.

Because studies suggest the best way to prevent the most disease due to HPV is to vaccinate as many girls and women as possible, the CDC did not add it to the recommended immunization schedules for males. However, boys and men ages 9 through 26 might choose to get immunized to prevent genital warts and anal cancer.

Park said other hurdles to HPV vaccination here and on the mainland include cost, which is not always covered by insurance, and the hassle of going back for three shots within the recommended six-month period.

Hawaii ranks sixth nationally in percentage of adolescent girls who get the first dose (63 percent), according to the CDCstudy, but fewer than 3 out of 4 girls complete the three-dose series as recommended.

Also, the two HPV vaccines — Gardasil and Cervarix — are relatively new, and some parents could be wary in the wake of claims — since discredited — that childhood immunizations can cause autism.

According to Park, no official public awareness campaigns were made when Gardasil went on the market in 2006. (Cervarix was approved by the Food and Drug Administration in 2009.)

“The (first) vaccine came out during the previous presidential administration (of George W. Bush), an office that was a bit conservative, so that could have played a factor,” Park explained.

The flu immunizations have become far more popular over the past 10 years, and Park feels HPV vaccinations will catch on as parents become more informed.

“A lot of parents don’t realize that vaccines are needed for this age group. Teens don’t typically see the doctor on a regular basis like kids under 5,” she said. “Vaccines aren’t just for infants.”

A report published in August by the Institute of Medicine, which advises the government, found the HPV vaccines are safe. Severe allergic reactions have been rare. Pain at the injection site is the most common side effect, Park said.

Ewa Beach resident Codie Kekona says her 17-year-old daughter Chael didn’t complain about any side effects. “It’s something that’s going to help her,” said Kekona. “Like all vaccines, the good outweighs the bad.”