Most cervical cancers are caused by human papillomavirus (HPV) — but widespread HPV vaccination 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., provides insight into the revolutionary cervical cancer vaccine.
What's the significance of the cervical cancer vaccine?
The original cervical cancer vaccine (Gardasil) was the first vaccine approved by the Food and Drug Administration (FDA) to prevent a cancer. Today, a second cervical cancer vaccine (Cervarix) also is available. 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 may 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.
What does the cervical cancer vaccine do?
Various strains of HPV, which spread through sexual contact, are responsible for most cases of cervical cancer. Both Gardasil and Cervarix specifically block two cancer-causing types of HPV — types 16 and 18 — to get at the root cause of the cancer. In essence, the vaccines stop cervical cancer before even the first step can begin.
Gardasil 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.
When should the cervical cancer vaccine be given?
HPV vaccination is recommended for girls ages 11 to 12, although Gardasil may be used in girls as young as age 9 and Cervarix may be used in girls as young as age 10. 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.
In addition, boys can be vaccinated with Gardasil between ages 9 and 18 to help prevent genital warts.
Both vaccines are 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 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.
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 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, however, researchers may find that three doses of the vaccine aren't necessary — or that a booster shot is needed years later.
