What’s This Vaccine for Human Papillomavirus?

A. In June 2006, the first vaccine marketed as a means to prevent certain types of cancer—Gardasil, manufactured by Merck—was approved by the Food and Drug Administration in the United States. This vaccine, which was later recommended to be given to all girls at 11 to 12 years of age, is highly effective in producing immunity to four different forms of human papillomavirus (HPV) that cause 70 percent of cervical cancer cases as well as HPV-associated warts (“genital warts” or condyloma) and a rare but serious condition in children, respiratory papillomatosis. A second HPV vaccine (Cervarix, manufactured by Glaxo-Smith-Kline), which was licensed and introduced to the U.S. in October 2009, produces immunity only to the two types of HPV associated with cervical cancer. Also in October 2009, Gardasil was approved by the Advisory Council on Immunization Practices (ACIP)—the immunization policy-making arm of the Centers for Disease Control and Prevention—for use in boys for the prevention of genital warts. These two vaccines, Gardasil and Cervarix, can decrease the risk of cervical cancer, a disease that leads to approximately 3,500 deaths annually in the U.S., as well as other cancers such as those of the vulva or vagina and possibly those in the mouth, throat or the anus. Yet these vaccines have been associated with controversy regarding their cost, the value they provide in relation to their cost, and concerns about offering vaccine protection to pre-teens for what are primarily sexually transmitted conditions.

Q. Is the vaccine cost-effective?

A. While vaccines in general are highly cost-effective when measuring the benefit to a population, cost-effectiveness decreases as the cost of the vaccine increases, or as the anticipated benefit to the population decreases. Both HPV vaccines are relatively expensive (approximately $120 per dose, or $360 for the series of three injections, not including physicians’ office visit or administration fees). Because the annual incidence of cervical cancer deaths is low thanks to the effectiveness of Pap screening and current treatment, the cost per year of life saved by vaccination is relatively high compared with current measures. Therefore the cost-effectiveness of the vaccines is low compared with other preventive measures; and while the Glaxo vaccine “may be given to boys nine through 26 years to reduce their likelihood of acquiring genital warts,” according to the ACIP, its routine use is not recommended because its use in boys does not meet the threshold for cost-effectiveness. However, approximately 500,000 people are diagnosed with genital warts in the U.S. each year and lose some quality of life. On May 28 the ACIP added the recommendation that girls ages 13 to 26 receive the three vaccine doses, although this ‘catch-up’ strategy is likely to be less cost-effective than the universal vaccination of 11 to 12 year-olds, due to the stronger (and probably longer-lasting) immune response in younger girls. In terms of the long-term effectiveness of the vaccine, data so far indicate the duration of immunity is at least four years, and probably longer. Those who have received the vaccine have only been followed up with for four to five years; therefore, routine booster shots are not recommended.

Q. How will giving the vaccine affect sexual behavior?

A. HPV is considered to be the most common sexually transmitted disease, and a high percentage of sexually active individuals will be exposed to the virus. The vaccine is most effective at preventing infection with the virus when given before any sexual exposure (although it is still recommend to be given to appropriately-aged individuals even if previous infection with HPV is known to have occurred). Parents who are concerned that their child may be more likely to engage in high-risk sexual behaviors because they feel protected from HPV should be aware (and make their child aware) that approximately 30 percent of cervical cancers are caused by HPV types that are not contained in either vaccine, and that the HPV vaccine has no effect on other sexually transmitted viruses for which medicine has no cure (e.g., herpes). Again, a main reason for giving the vaccine to young girls (rather than waiting until they begin sexual activity) is that the immune response is likely to last longer. Given the statistics about the age at which sexual activity begins (about 20 percent of adolescents have had sex by the age of 14, and about 50 percent by 17 years of age), giving the vaccine at an early age
makes sense.

Writtten by Christine C. Matson, MD