Get answers about the cervical cancer vaccine, including how the vaccine works and who should be vaccinated.

By Mayo Clinic staff

Bobbie Gostout, M.D.

A vaccine that offers protection from the virus responsible for most cases of cervical cancer is the latest addition to the official childhood immunization schedule. Here, Bobbie Gostout, M.D., an HPV infection expert and gynecologic surgeon at Mayo Clinic, Rochester, Minn., provides insight into this revolutionary cervical cancer vaccine.

The cervical cancer vaccine (Gardasil) is the first vaccine approved by the Food and Drug Administration (FDA) designed to prevent a cancer. In the United States — where cervical cancer strikes about 10,000 women a year and causes nearly 4,000 deaths — the impact of the cervical cancer vaccine will be tremendous. Worldwide, the impact may be even greater. According to the World Health Organization, about 510,000 new cases of cervical cancer are reported each year.

The tragedy of cervical cancer is that it often strikes when a woman is still young. She may be trying to raise her family or maybe she hasn't had children yet. Cervical cancer treatment may make future fertility impossible.

Various strains of the human papillomavirus (HPV), which spreads through sexual contact, are responsible for most cases of cervical cancer. The cervical cancer vaccine specifically blocks two cancer-causing types of HPV — types 16 and 18 — to get at the root cause of the cancer. In essence, the cervical cancer vaccine stops cervical cancer before even the first step can begin.

The cervical cancer vaccine also blocks HPV types 6 and 11, which are not associated with cervical cancer but are associated with genital warts and mild Pap test abnormalities.

 

The vaccine is recommended for girls ages 11 to 12, although it may be used in girls as young as age 9. This allows a girl's immune system to be activated before she's likely to encounter HPV. Vaccinating at this age also allows for the highest antibody levels. The higher the antibody levels, the greater the protection.

The vaccine is given as a series of three injections over a six-month period. The second dose is given two months after the first dose, followed four months later by the third dose.

Experts at the Centers for Disease Control and Prevention (CDC) recommend a catch-up immunization for girls and women ages 13 to 26 who haven't been vaccinated or who haven't completed the full vaccine series. By vaccinating this catch-up group, as well as the younger girls, we'll see the positive effects of the cervical cancer vaccine that much sooner.

We really don't know that three doses are necessary because we don't know what antibody levels provide adequate protection from HPV. In early clinical trials, researchers observed that the antibody levels in women continued to go up 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 to get the greatest HPV protection for the longest possible time — years or even decades.

Over time, we may find that three doses of the vaccine aren't necessary, or we may discover that a booster shot is needed years later. Those are details we just don't know right now.

Yes. In clinical trials, the vaccine was effective in a group of sexually active women age 26 or younger, some of whom had already been infected with one or more types of HPV. There's a caveat, however. The cervical cancer vaccine blocks HPV types 6, 11, 16 and 18, but only if you haven't been exposed to those particular types of HPV. The more sexual partners you've had, the greater your chance of having been exposed to multiple types of HPV — including HPV types 6, 11, 16 and 18.

Some experts encourage women ages 18 to 26 to review their sexual history with their doctors to determine if there's a reasonable chance of benefiting from the vaccine. Others support the CDC's recommendation of universal vaccination for women ages 18 to 26.

The cervical cancer vaccine has proved to be remarkably safe. Over 16 million doses have been distributed in the U.S. The most common complaint is soreness at the injection site, the upper arm. Low-grade fever or flu-like symptoms also are common. Sometimes dizziness or fainting occurs after the injection, especially in adolescents. Overall, the effects are usually mild.

However, some serious side effects have been reported, including a severe allergic response (anaphylaxis); neurological conditions, such as paralysis, weakness and brain swelling; and death. The FDA continues to monitor all such reports. To date, almost all reports of such adverse side effects appear to have occurred around the time of vaccination by chance. They don't appear to be caused by the vaccination itself.

Monitoring is ongoing with this vaccine, as with all newer vaccines. Women and girls should remain seated in the clinic where they receive the vaccine for 15 minutes after the injection to reduce the risks of fainting or of an allergic reaction.

The cervical cancer vaccine is part of the routine childhood vaccines schedule. Whether or not a vaccine becomes a requirement for school is decided on a state-by-state basis. Remember, the greater the number of girls and women vaccinated, the greater the benefit we'll see from the cervical cancer vaccine.

Absolutely. And this is a really important point. 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.

HPV spreads through sexual contact. To protect yourself from HPV, use a condom every time you have sex. It's also important to limit your number of sexual partners. Not smoking helps, too. Smoking doubles the risk of cervical cancer.

To detect cervical cancer in the earliest stages, see your doctor 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; foul-smelling watery or bloody vaginal discharge; pelvic pain; or pain during sex.