A study of the sexually transmitted human papillomavirus has found that 3.4% of females in the U.S. ages 14 to 59 are infected with at least one of four viral types that could be blocked by the controversial vaccine Gardasil, researchers reported Tuesday.
The study found that 3.1 million females have HPV types 6 or 11, which cause about 90% of genital warts cases, or types 16 or 18, which account for 70% of the roughly 11,000 cervical cancer cases diagnosed each year in the U.S. Cervical cancer kills about 4,000 women in the U.S. annually.
The Gardasil vaccine is nearly 100% effective in blocking the viruses, but because it does not work against existing infections, it should be given before females become sexually active.
The study, published in the Journal of the American Medical Assn., was based on the 2003-2004 National Health and Nutrition Examination Survey, which collected vaginal swabs and demographic information from 2,026 females ages 14 to 59.
The researchers looked for infections from the more than 30 types of HPV. They found that 26.8%, or about 24.9 million females, had some type of HPV infection at the time of the survey. The majority of infections clear within two years, according to the report.
Disease prevalence was highest among women ages 20 to 24, where researchers found 44.8% had an infection. The virus was detected in 24.5% of females ages 14 to 19 and in 27.4% of women ages 25 to 29. The lowest prevalence, 19.6%, was found in women 50 to 59.
“Women should know just how common of an infection this is,” said lead author Dr. Eileen F. Dunne, an epidemiologist with the national Centers for Disease Control and Prevention in Atlanta.
The study’s key finding was on the prevalence of the four viral types targeted by Gardasil, produced by Merck & Co.
Last year, the CDC recommended Gardasil for all girls ages 11 and 12. At least 20 states are weighing making the vaccine mandatory for preteen girls, and in Texas, Gov. Rick Perry has done so by executive order.
Some people have opposed making the vaccine mandatory for school entry on the grounds that it negates parental choice. Other opponents worry that a vaccine against a sexually transmitted disease might encourage promiscuity. In Texas, lawmakers have introduced a bill to overturn the governor’s action, and some parents have filed suit.
Lawmakers and parents have also raised concerns about the cost of the vaccine, which is given in three shots at a total cost of about $500, factoring in the cost of doctor’s visits.
Patti Gravitt, associate professor of epidemiology at Johns Hopkins Bloomberg School of Public Health, who was not involved in the study, said that even though the prevalence of the four HPV types was relatively low, the data supported the cost-effectiveness of Gardasil due to the high cost of treating cancer.