Many more women than previously thought are infected at some time in their lives, and particularly in the early years of sexual activity, with the human papillomavirus (HPV), according to a study published in the February 28 issue of the Journal of the American Medical Association.

Using data from the National Health and Nutrition Examination Survey (NHANES), in which females aged 14 to 59 years were examined at mobile centers and provided self-collected vaginal swab specimens, the study found the overall prevalence of HPV in women aged 14 to 24 years was 33.8 percent.

Broken down by age groups, HPV was prevalent in 24.5 percent of women ages 14 to 19 years. Prevalence then rose sharply, to 44.8 percent, in women 20 to 24 years old. For women aged 25 to 59 years, HPV prevalence ranged from 19 percent to 25 percent.

 The report indicates that HPV types 6 and 11, which are known to cause approximately 90 percent of genital warts, and types 16 and 18, which cause approximately 70 percent of cervical cancers, were detected in only 3.4 percent of the female participants. HPV-16 and HPV-18 were found in 1.5 percent and 0.8 percent of the women, respectively.

A newly available HPV vaccine, Gardasil, produced by the pharmaceutical company Merck, protects against HPV types 6, 11, 16, and 18.The vaccine is currently the subject of controversy over whether states should mandate vaccination of 11- to 12-year-old girls against HPV as a condition of school attendance. Currently, one state—Texas—has mandated vaccination and another—Virginia—is considering such a proposal. Some 20 states are considering whether to adopt similar mandates, according to the National Conference of State Legislatures.

Here is some of the information about the human papillomavirus that has emerged from recent studies:

• HPV is estimated to be the most common sexually transmitted infection, with prevalence highest among young persons within the first few years after sexual debut.
• General HPV types are characterized according to their epidemiological association with cervical cancer. Infection with low-risk types of the virus can cause benign or low-grade changes in cells of the cervix, genital warts, and recurrent respiratory papillomatosis. High-risk types of the virus can cause cervical, anal, and other genital cancers. High-risk HPV types are detected in 99 percent of cervical cancers.
• Although HPV infection is common, approximately 90 percent of infections clear within two years as a woman’s immune system rallies against the virus.
• Clinical studies of the quadrivalent HPV vaccine now available show close to 100 percent efficacy in preventing infection and disease (cervical cancer precursors and genital lesions) associated with four specific types of the virus.

In an editorial accompanying the research report, the Journal notes that it is very difficult to assess the prevalence of HPV in the United States, but the data reported in the current study are consistent with other studies that have found young women at greater risk of HPV infection than older women.

The editorial notes that the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention has provisionally recommended the HPV vaccine for adolescent girls between the ages of 11 and 12 years, with catch-up vaccination for those between 13 and 26 years. The editorial also points out that it will now be important to assess the cost-effectiveness of the vaccine, using the new prevalence data.

The research report, “Prevalence of HPV Infection Among Females in the United States,” and the editorial, “Estimating the Population Prevalence of HPV,” were published in the February 28, 2007, issue of the Journal of the American Medical Association.