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The case for and against immunizing boys against HPV:
Widespread immunization of girls and boys against the human papillomavirus could fully eradicate types 16 and 18 of the virus. If we miss half the equation by leaving the boys out of our vaccination strategy, that type of public health success will not be possible.
The benefits of human papillomavirus (HPV) vaccination in boys are numerous. While protecting women from HPV and the morbidity and mortality associated with cervical cancer is a significant motivation for male vaccination, males would also accrue their own health benefits through vaccination. For example, approximately 12% of oral pharyngeal cancers are caused by HPV types 16 and 18, which also cause some penile and anal cancers. Also, 90% of genital warts are caused by HPV types 6 and 11, which can occur in boys as well as in girls; while not life-threatening, genital warts are certainly anxiety provoking. In addition, one out of four girls and one out of six boys is the victim of sexual abuse by age 20. That's a high number of young people for whom prevention would be relevant.
If we want to achieve herd immunity with HPV, we really need to vaccinate both sexes. There's also a larger message from society in how we choose to formulate our vaccination strategy. If we don't vaccinate boys, we are saying as a society that females alone have the responsibility for society's sexual health.
Men also have a stake in the health of their future sexual partners. While boys may be only 11 or 12 years old when their parents consent to HPV vaccination on their behalf, these boys and their parents will not want their future partners or offspring to be exposed to life-threatening HPV.
The cost-effectiveness estimates for vaccinating boys are not compelling at this point. However, the public health benefit is clear and the medical risks associated with vaccination are extremely low. In fact, the experience with girls in the United States has been excellent, with fewer adverse events reported for the HPV vaccine than for most other common vaccines.
The issue of immunizing males against HPV often comes down to whether they should receive the vaccine to protect females. Doing so is honorable and even reasonable, but at this point there is little evidence suggesting that this is cost effective.
Early cost-benefit analyses of this idea showed that a large number of males would need to be immunized to achieve even a minimal increase in protection for females. At the same time, adding males to the equation would significantly increase the cost of the immunization program. So, until there are more compelling data to show that immunizing males will protect large numbers of females, the right thing to do is to immunize the people we are trying to protect—girls and women themselves.
This said, there are other compelling reasons to consider vaccinating males. Newer data are beginning to show that HPV does more in men than might have been appreciated just a decade ago. A significant portion of head and neck cancers, anal cancers, and cancer of the larynx are caused by HPV. When you start adding up the number of cases of cancers in males attributable to HPV, you end up with roughly the same number as that of cervical cancer cases in the United States. Not to be forgotten is the significant morbidity associated with genital warts. So the reasons to immunize males will likely have more to do with protecting males against the diseases they get, rather than protecting women from cancer.
The catch with male immunization is that the studies showing that HPV vaccines prevent these cancers in men do not yet merit changing our vaccination strategy. When the data are available, I expect we will have sound reasons to immunize males against HPV. But studies showing that these vaccines prevent genital warts have not yet been published, and it will be perhaps 3–5 years before we see strong evidence related to cancer prevention benefits.