A vaccine that prevents cervical cancer should also be given to boys in their preteen years, a federal panel announced on October 25. The move acknowledges a raft of studies showing that boys and men would benefit from the immunization, which protects against several cancers caused by the human papillomavirus, or HPV.
By recommending the vaccine for boys starting at age 11 or 12, the Advisory Committee on Immunization Practices — whose recommendations serve as guideposts for doctors — places boys on nearly the same footing as girls, who are already advised to get the vaccine. HPV can cause genital warts and cancers of the vagina, penis, vulva, throat and anus.
Further bolstering a wider role for the vaccine, scientists report in the Oct. 27 New England Journal of Medicine that in men who have sex with men the vaccine limits the formation of precancerous anal lesions, a kind of cell growth that can lead to anal cancer in this high-risk group.
HPV rarely causes symptoms, but it is the most common sexually transmitted infection in the United States with more than 6 million new infections each year. Some of the strongest evidence supporting an expansion of the vaccine guidelines to males comes from studies of cancers of the throat and tonsils. Roughly 80 percent of such cancers are traceable to an HPV infection, says Robert Haddad, an oncologist at the Dana-Farber Cancer Institute in Boston.
“I expect we will see more use of this vaccine now,” Haddad says. The throat cancers linked to HPV infections contracted by oral sex “have reached epidemic levels and incidence is rising,” he says.
While less common, anal cancer is also increasing at a rate of 2 percent per year, data from the Food and Drug Administration show.
In the new study, researchers tested the HPV vaccine Gardasil in 602 healthy men who have sex with men ages 16 to 26 in seven countries. Gardasil triggers an immune response against two cancer-causing HPV types —16 and 18 — and protects against two other types that cause genital warts.
The scientists randomly assigned the volunteers to get the standard three-shot course of Gardasil or placebo shots. During the next three years, check-ups for precancerous anal lesions caused by HPV types covered by the vaccine revealed about half as many in the vaccinated men as in those getting placebos.
Some of the volunteers had had an HPV infection before entering the study. When these volunteers were excluded from the analysis, the remaining men who got the vaccine had about one-fourth as many lesions caused by HPV types covered by the vaccine as their unvaccinated counterparts.
The vaccine doesn’t seem to work against an HPV type that has already infected an individual, says study coauthor Joel Palefsky, an infectious disease physician at the University of California, San Francisco. Thus, findings from the unexposed men in the new study provide “the kind of data we would see if we vaccinated people early on as 11- and 12-year-olds,” he says. When it became clear that the vaccine offered a benefit, the study was stopped and all volunteers were offered the vaccine.
HPV 16 and 18 are responsible for about 70 percent of cervical cancers and 90 percent of anal cancers. HPV 16 accounts for most throat cancers. Expanding the vaccine recommendation to boys “is a major step forward in public health,” Palefsky says.
The National Institutes of Health funded the new study with Merck, which makes Gardasil.