Increasing Number of Boys Vaccinated Against HPV Could Protect More People at the Same Price
Public health programs that devote a portion of their funding to encourage more boys to be vaccinated against human papillomavirus (HPV)—rather than merely attempting to raise coverage among girls—may ultimately protect more people for the same price, a study from Duke University suggests. The findings appear in an article by Ryser et al in Epidemics.
Whether vaccinating boys against HPV in addition to girls would only divert scarce resources from a campaign originally designed to help prevent cervical cancer has been hotly debated. But with HPV-related cancers in men on the rise, and HPV vaccine coverage in U.S. girls stagnating well below the critical levels needed to ensure that most people are protected, researchers have been reexamining the case for a girls-only approach.
Not Contained to Cervical Cancer
Although HPV is most frequently associated with cervical cancer, women are not the only ones at risk. The Centers for Disease Control and Prevention estimates that one-third of the 27,000 cases of cancer HPV causes in the United States each year occur in men, where it can cause cancers of the throat, tongue, tonsils, penis, and anus. Studies suggest that HPV-related throat and mouth cancers are on the rise in the United States and could outnumber HPV-related cervical cancers by 2020.
Many of these cancers could be prevented with vaccination. But despite recommendations that both boys and girls aged 11 to 12 should receive the HPV vaccine, only 37% of girls and 14% of boys in the United States have received all three shots in the HPV vaccine series—much lower than the proportion needed to keep the disease in check.
Study Details
To find out whether different strategies for allocating public funds might protect more people, Duke mathematicians Marc Ryser, PhD, and Kevin McGoff, PhD, and Evan Myers, MD, MPH, Professor of Obstetrics and Gynecology, and colleagues developed a mathematical model of HPV transmission among sexually active 14 to 18 year olds. They then compared the effectiveness of HPV vaccination campaigns based on different cost scenarios.
One set of scenarios reflected the costs of vaccinating more people based on the per-dose price of the vaccine. Another set of scenarios also accounted for the patient education costs that could be required to reach people who are less willing to have their children vaccinated.
Over the past 3 years, HPV vaccination coverage in girls has stagnated. Studies suggest that 44% of U.S. parents are reluctant to vaccinate their kids against a sexually transmitted infection before their child becomes sexually active—even though the vaccine works best if given before there is any chance of exposure, when there is still time to build up immunity.
Boosting coverage in girls to sufficient levels to protect everyone could become increasingly expensive, Dr. Ryser said, especially as the pool of willing parents shrinks, and only the more skeptical parents remain.
“Imagine that 100 parents are offered HPV vaccines for their children,” said coauthor Dr. Myers. “Some fraction will be willing to have their child vaccinated without any questions, some won't have their child vaccinated under any circumstances, and the rest will be in between.”
“Along the spectrum of “whatever you say, doctor” to “I don't believe in any vaccinations,” families who are currently unvaccinated are closer to the resistant end of the spectrum, and so it takes more work and costs more money to try to persuade them," said Dr. Myers.
Next Steps
Real-world data on actual patient education costs are needed before the results can be translated into policy, the authors said.
But their analysis suggests that public health officials may actually be able to protect more people for the same price, by shifting some funds to encourage vaccination of boys, since the fraction of parents willing to vaccinate has yet to be exhausted among boys.
“The gender with the lowest coverage is the low-hanging fruit,” Dr. Ryser said. “Stagnating vaccination rates, coupled with parental opposition, suggest that it could cost less to raise coverage in boys from, say, 14% to 15%, than to raise coverage in girls from 37% to 38%.”
“Making that trade-off would be beneficial to the entire population,” said coauthor Dr. McGoff.
Dr. Ryser is the corresponding author for the Epidemics article.
This study was supported by the National Institutes of Health, the National Science Foundation, and Duke University. Dr. Myers serves as a consultant to Merck, Inc, manufacturer of the HPV vaccine Gardasil. Merck was not involved in any way with this study.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
