The vaccine for human papillomavirus (HPV) can prevent 90 percent of genital warts in men when offered before exposure to the four HPV strains covered by the vaccine, says a new multi-center study led by H. Lee Moffitt Cancer Center and UCSF.
The four-year, international clinical trial, which also found a nearly 66 percent effectiveness in the general population of young men regardless of prior exposure to these strains, provides the first reported results of using the HPV vaccine as a prophylactic in men.
While the HPV vaccine was approved in 2006 for girls to prevent cervical cancer, the vaccine's benefit for young men was not initially addressed. Yet infection and diseases caused by HPV are common in men, the researchers said, including genital warts, which are one of the leading sexually transmitted diseases (STD) for which treatment is sought nationwide.
"This is an exciting development in the STD world," said Joel Palefsky, a UCSF professor of medicine who co-led the research along with epidemiologist Anna R. Giuliano, from the H. Lee Moffitt Cancer Center and Research Institute, in Tampa, FL. "It shows that if we vaccinate males early enough, we should be able to prevent most cases of external genital warts in this population."
While warts are often considered an annoyance, rather than a life-threatening disease such as cervical cancer, Palefsky noted that warts are a common problem in young people and are often associated with depression, social stigma and loss of self-esteem. Complications of wart treatments are also quite common, he said.
The double-blind study included 4,065 healthy men aged 16-26 years, spanning 71 sites in 18 countries. Of those patients, 85 percent reported having exclusively female sexual partners, with the remainder self-identified as having sex with men.
The men were tested at the onset of the trial for previous exposure to each strain and were randomly selected to receive either a placebo or a vaccine that targeted HPV strains 6, 11, 16 and 18. Men with a history of anal or genital warts or lesions were excluded. Participants then received six follow-up examinations over the following three years to assess the vaccine's effectiveness.
In addition to preventing warts, the vaccine also effectively prevented HPV-persistent infection in 86 percent of the participants without previous exposure.
"This is the first study to show that this vaccine works in boys," Giuliano said. "As long as we have a poor record of vaccinations in girls, boys should also be vaccinated."
Findings can be found in the Feb. 3 issue of the New England Journal of Medicine.