Since it became available in the United States in 2006, the Human Papillomavirus (HPV) vaccine has been a source of debate, with proponents lauding it as a substantial gain in the fight against cancer, and opponents concerned with its implications for sexual activity among youth. With the U.S. Food and Drug Administration’s recent approval of Gardasil-9 — a vaccine that protects against nine of the most common strains of HPV that account for approximately 90 percent of cervical, vulvar, vaginal and anal cancers — there is both a renewed interest and concern that calls for a nuanced and comprehensive review of the science.
HPV is the most common sexually transmitted infection in the United States, with nearly all sexually active men and women believed to contract at least one form of it during their lifetime. According to the U.S. Centers for Disease Control and Prevention (CDC), an estimated 79 million Americans have HPV, and about 14 million become newly infected annually. While most infections clear the body within two years, some can persist and result in genital warts, cervical cancer or other types of cancers in men and women. Of the many HPV strains that exist, HPV types 16 and 18 have been identified as high risk, accounting for about 70 percent of all cervical cancer, as well as a large proportion of other HPV-related cancers.
While cervical cancer was previously a leading cause of death among women in the U.S., death rates declined substantially after the introduction of the Pap test in the 1950s. Nevertheless, according to the CDC, more than 12,000 women in the U.S. are diagnosed with cervical cancer each year, and more than 4,000 die from it. Public discourse around HPV tends to focus on the health of women because they disproportionately bear the burden of its health consequences. However, men also face substantial risk, particularly as it relates to oral and anal cancers.
Although screening procedures are in place for early detection of cervical cancer, there are no comparable strategies to identify HPV-related cancer in its early stages for men. Consequently, the administration of a vaccine to prevent infection and transmission presents an important line of protection. Currently, the HPV vaccine is administered over a course of three injections, which must be completed within six months to confer full protection. A 2012 review of clinical trials of HPV vaccines shows that vaccines designed to protect against two or four of the most common strains have very high efficacy rates, ranging between 90 percent and 100 percent. For that reason, large public health efforts have focused on improving vaccination rates before boys and girls become sexually active.
Today, both the CDC and American Academy of Pediatrics recommend routine vaccination against HPV for all 11-year-olds and 12-year-olds in the U.S. Although the early age of vaccination has been a source of public debate, medical recommendations are based partly on evidence that shows that antibody responses are highest during this age period. Also, it is a good idea to vaccinate adolescents before they come into contact with the virus as the vaccine is not effective against HPV types that already have been acquired. Despite such recommendations from medical professionals, vaccination completion rates remain low — 40 percent for girls and 20 percent for boys in 2014. That is substantially lower than the vaccination rate for tetanus, diphtheria, and pertussis and the vaccination rate for meningitis among members of the same age group.
Below are a series of studies that will help journalists understand and explain this important health topic from a variety of angles, including vaccine safety and racial and gender disparities in vaccination rates. Beat reporters can find related reports and statistics from organizations such as the CDC, National Cancer Institute and World Health Organization.
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