Despite Benefits, HPV Vaccination Rates Remain Too Low
Despite impressive efficacy for the human papillomavirus (HPV) vaccine reducing the prevalence of high-risk oral HPV infections by 88 percent, many young adults still are not getting the vaccine – sparking concern in the health community.
Results from one of the first large studies to explore the impact of HPV vaccination on oral infections show that their prevalence among vaccinated young adults was 0.11 percent for HPV types 16, 18, 6 and 11, compared with 1.61 percent for unvaccinated individuals. Prevalence of the four HPV types covered by the vaccine was eliminated in men who had been vaccinated compared with those who had not been vaccinated (0.0 percent vs 2.13 percent). Prevalence of the 33 nonvaccine HPV types was similar between the two groups (3.98 percent vs. 4.74 percent).
HPV vaccination is currently indicated for the prevention of cervical, vulvar and vaginal cancers in women, and anal cancers in both women and men. It has not been clear, however, whether the vaccines could reduce incidence of oral cancers related to oral HPV infection.
“Our data indicate that HPV vaccines have tremendous potential to prevent oral infections,” said Maura L. Gillison, M.D., Ph.D., professor of medicine at the University of Texas MD Anderson Cancer Center, who discussed the results during a press conference May 17 in advance of the 2017 ASCO Annual Meeting. “While we were encouraged that there was a notable impact of the vaccine on oral HPV infections among vaccinated individuals, that benefit was modest overall and lower than we would hope in men due to low vaccine uptake.”
Gillison and colleagues reviewed data collected from 2011 to 2014 in the National Health and Nutrition Examination Survey (NHANES) of Americans. Investigators compared HPV infection rates for 2,627 men and women aged 18 to 33 who reported receiving at least one dose of HPV vaccine with a similarly aged cohort who was not vaccinated. HPV infection was detected from oral rinse samples collected by mobile health facilities and then tested for HPV in the laboratory.
Although the vaccine appears to show clear efficacy in preventing HPV infections, uptake in the population at large remains low. The vaccine was approved for young women aged 9 to 26 in 2006 and young men aged 9 to 21 in 2011. However, from 2011 through 2014, only 18.3 percent of adults received at least 1 dose of the vaccine before age 26. Young men were vaccinated at one-quarter the rate of young women (6.9 percent vs 29.2 percent).
Researchers estimate that the vaccine reduced oral HPV infections by 17 percent overall during the study period, representing nearly 170,000 cancers. As expected, the impact was greater among women compared with men, 25 percent versus 6.9 percent.
Because uptake has been poor, the vaccine hasn’t had the full effect that it could. Gillison said that with 100 percent coverage, the vaccine would have prevented an estimated 927,401 cancers.
“The HPV vaccine is one of the most important advances in cancer prevention in the last several decades. Parents who choose to have their children vaccinated against HPV should realize that the vaccine may provide additional benefits, such as prevention of oral HPV infections linked to oral cancers.”
There is some good news; uptake is higher now than during the study period. “Recent data indicate that in individuals under the age of 18, 60 percent of girls have received the vaccine and 40 percent of boys,” she said.
Emily Ko, M.D., assistant professor of gynecologic oncology at the University of Pennsylvania, reviewed the data. Despite clear evidence of efficacy, she said that patients aren’t getting the vaccine for a variety of reasons.
“There are multiple barriers — social, logistical, knowledge and access,” she said. “There are cultural values and beliefs, as well as fear and stigma. There is still some apprehension about whether even talking about this vaccine or getting this vaccine could encourage sexual activity.”
“We have to think about how to expand knowledge about the benefits of the vaccine and how to educate people about the risks,” Ko continued. “I think people are still scared about the side effects of the vaccine. There have been studies that looked at whether getting the vaccine increases sexual activity. I don’t think that is the case, but there should be awareness that this is not the purpose of the vaccine. We have to correct those misbeliefs.”