Cervical cancer vaccine: Who needs it, how it works

Who needs the cervical cancer vaccine? How many doses? Can boys be vaccinated, too? What about side effects? Get answers to these questions and more.

 Bobbie Gostout, M.D.

Most cervical cancers are caused by the sexually transmitted infection human papillomavirus (HPV). Widespread HPV immunization, however, could reduce the impact of cervical cancer worldwide. Here, Bobbie Gostout, M.D., an HPV infection expert and gynecologic surgeon at Mayo Clinic, Rochester, Minn., discusses the cervical cancer vaccine.

What does the cervical cancer vaccine do?

Various strains of HPV, which spread through sexual contact, cause most cases of cervical cancer. Two cervical cancer vaccines have Food and Drug Administration (FDA) approval in the U.S. — Gardasil and Cervarix. Both vaccines can prevent most cases of cervical cancer if given before a girl or woman is exposed to the virus.

In addition, both can prevent most vaginal and vulvar cancer in women, and Gardasil can prevent genital warts in women and men.

Who is the cervical cancer vaccine for and when should it be given?

The cervical cancer vaccine is recommended for girls and boys ages 11 to 12, although it may be given as early as age 9. It's important for boys and girls to receive the vaccine before they have sexual contact and are exposed to HPV. Once infected with HPV, the vaccine may not be as effective.

If not fully vaccinated at ages 11 to 12, the Centers for Disease Control and Prevention (CDC) recommends that girls and women through age 26 and boys and men through age 21 receive the vaccine. However, men may receive the HPV vaccine through age 26 if desired.

Both vaccines are given as a series of three injections over a six-month period. The second dose is given one to two months after the first dose, and the third dose is given six months after the first dose.

The cervical cancer vaccine isn't recommended for pregnant women or people who are moderately or severely ill. Tell your doctor if you have any severe allergies, including an allergy to yeast or latex.

Why are three doses of the cervical cancer vaccine needed?

Researchers don't yet know what antibody levels provide adequate protection from HPV. In early clinical trials, researchers observed that women's antibody levels continued to increase with each of the three doses of the vaccine. Since antibody levels inevitably fall once you stop getting a vaccine, it makes sense to start with high antibody levels and attempt to get the greatest HPV protection for the longest possible time — years or even decades.

Over time, however, researchers may find that three doses of the vaccine aren't necessary — or that a booster shot is needed years later.

Does the cervical cancer vaccine offer benefits if you're already sexually active?

Yes. In clinical trials, Gardasil and Cervarix were effective in groups of sexually active women age 26 or younger, some of whom had already been infected with one or more types of HPV. However, Gardasil and Cervarix only protect you from specific strains of HPV to which you haven't been exposed. The more sexual partners you've had, the greater your chance of having been exposed to multiple types of HPV.

Does the cervical cancer vaccine carry any health risks or side effects?

Overall, the effects are usually mild. The most common side effects of both HPV vaccines include soreness at the injection site (the upper arm), headaches, low-grade fever or flu-like symptoms. Sometimes dizziness or fainting occurs after the injection, especially in adolescents. Remaining seated for 15 minutes after the injection can reduce the risk of fainting. In addition, Cervarix may also cause nausea, vomiting, diarrhea or abdominal pain.

Serious side effects — including a severe allergic response (anaphylaxis), and neurological conditions, such as paralysis, weakness and brain swelling — have been reported in a small number of women. The FDA continues to monitor all such reports. To date, however, almost all reports of such adverse side effects appear to have occurred by chance around the time of immunization. They don't appear to have been caused by the vaccine itself.

Is the cervical cancer vaccine required for school enrollment?

The cervical cancer vaccine — either Gardasil or Cervarix — is part of the routine childhood vaccines schedule. Whether or not a vaccine becomes a school enrollment requirement is decided on a state-by-state basis.

Do women who've received the cervical cancer vaccine still need to have Pap tests?

Yes. The cervical cancer vaccine isn't intended to replace Pap tests. Routine screening for cervical cancer through regular pelvic exams and Pap tests remains an essential part of a woman's preventive health care.

What can you do to protect yourself from cervical cancer if you're not in the recommended vaccine age group?

HPV spreads through sexual contact. To protect yourself from HPV, use a condom every time you have sex and limit your number of sexual partners. In addition, don't smoke. Smoking doubles the risk of cervical cancer.

To detect cervical cancer in the earliest stages, see your health care provider for regular pelvic exams and Pap tests. Seek prompt medical attention if you notice any signs or symptoms of cervical cancer — vaginal bleeding after sex, between periods or after menopause, pelvic pain, or pain during sex.