Source: www.washingtonpost.com
Author: Erin Blakemore

About half of American teenagers have been vaccinated against the human papillomavirus (HPV), the most common sexually transmitted infection in the United States. Should adult women follow suit?

Yes, says Lauri Markowitz, a Centers for Disease Control and Prevention medical epidemiologist who has worked with the advisory committee that makes national vaccination recommendations. “Women 18 to 26 should be vaccinated.”

There’s good reason to follow that recommendation. According to the American Cancer Society, about 12,820 new cases of cervical cancer will be diagnosed in U.S. women this year and more than 4,000 will die of the disease. HPV is thought to be responsible for more than 90 percent of all cervical and anal cancers in men and women. The virus also causes vaginal, vulvar and throat cancers and genital warts.

Although the majority of HPV infections do not cause cancer — most people with an infection never show any symptoms, and infections usually go away on their own — some strains are particularly dangerous. Gardasil 9, the newest HPV vaccine approved by the Food and Drug Administration, protects against nine such strains and, researchers say, may be able to prevent up to 90 percent of cervical cancers. (Older vaccines protect against fewer strains of HPV.)

However, confusion about the way HPV vaccines protect against infection can deter some women. Gardasil 9 is approved for women up to age 26. Like other vaccines, it spurs the body’s immune system to defend itself against a virus. The FDA and CDC say the HPV vaccines are safe and extremely effective: HPV rates in women ages 14 to 19 years fell 64 percent within six years of the vaccine’s introduction in the United States in the mid-2000s and 34 percent in women ages 20 to 24.

The vaccines are most effective if administered before a woman becomes sexually active. The longer a woman has been sexually active and the more partners she has had, the more opportunities she has had to become infected with an HPV strain that overlaps with the vaccine. If she is vaccinated at an older age, the vaccine may be less effective in lowering her cancer risk, Markowitz says. The vaccine can’t clear any HPV that has taken hold; it can only prevent future infection. So essentially if you already have been exposed to one of the strains it protects against, it will be useless against that strain.

That doesn’t mean it’s useless to get vaccinated if you’re older than the recommended age of 11 or 12, Markowitz says. “Your chances of being protected are decreasing, but you will still have some protection,” she says. Although the likelihood that a sexually active woman has been infected with one of the strains the vaccine protects against increases as a woman has more partners, those who didn’t receive the vaccine at the recommended age are still urged to get vaccinated to increase the odds of protection.

Some insurance does not cover the vaccine for those older than 18 — the shots can be costly, though the manufacturer may provide assistance — but it really varies across the board.