Vaccination against human papillomavirus (HPV) appears to be highly effective at preventing oral infection with oncogenic types of the virus, based on the results of a cohort study of a nationally representative sample of more than 2,600 U.S. young adults.
“HPV-positive oropharynx cancer is the fastest rising cancer among young white men in the United States. Over 90% of these cancers are caused by HPV type 16,” said senior study author Maura L. Gillison, MD, PhD, who conducted the research at Ohio State University, Columbus. “HPV 16 is one of the types covered in currently recommended HPV vaccines that have been shown to be safe and effective in the prevention of anogenital infections and associated cancers.
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Results of the study showed that only about a sixth of the young adults surveyed between 2011 and 2014 had received at least one dose of an HPV vaccine. But relative to peers who had not received any doses, these young adults had an 88% lower prevalence of oral infection with HPV types 16, 18, 6, and 11, which are covered by vaccines; in particular, prevalence was 100% lower, with complete absence of these infections, in vaccinated young men, compared with unvaccinated young men, Dr. Gillison said in a presscast leading up to the annual meeting of the American Society of Clinical Oncology.
Analyses further suggested that based on levels of vaccine uptake seen in 2014 in the population, the vaccine was preventing only about 17% of the total of approximately 927,000 preventable oral infections with these virus types in that year.
“Our data indicate that HPV vaccines have tremendous potential to prevent oral infection,” said Dr. Gillison, noting that they are already strongly recommended by numerous health and medical organizations. Unfortunately, at the time of the study, “low vaccine uptake limited the population impact of the vaccine.”
However, there is now “considerable optimism,” she said, because recent data have shown that 60% of girls and 40% of boys younger than 18 have received at least one dose of HPV vaccine, marking a major increase in uptake.
“We can’t say that this is cause effect, the impact of these vaccines on infection, because this isn’t a prospective clinical trial,” she acknowledged. “Nevertheless, we can conclude that HPV vaccination may have additional benefits beyond prevention of anogenital cancers.”
The findings are encouraging in that they suggest it will be possible to avert infection-induced oropharyngeal cancer, according to ASCO President-Elect Bruce E. Johnson, MD, who is also chief clinical research officer at the Dana-Farber Cancer Institute and professor of medicine at Harvard Medical School, both in Boston.
“This certainly shows that in the target population to get vaccination, you can indeed prevent the infection, which is one of the first steps that would eventually potentially lead to cancer,” he said.
In the study, Dr. Gillison and her colleagues analyzed data from 2,627 men and women aged 18-33 years who participated in the National Health and Nutrition Examination Survey in the years 2011-2014. Oral rinses were collected as part of the survey to assess HPV infection.
The results showed that 18% of the young adults overall reported having received at least one dose of HPV vaccine, although receipt was much higher among young women than among young men (29% vs. 7%).
The prevalence of oral infection with HPV types 16/18/6/11 was sharply lower for these vaccinated young adults, compared with unvaccinated peers in the cohort as a whole (0.11% vs. 1.6%; P = .008). In a sex-stratified analysis, the reduction was especially striking among men (0% vs. 2%, P = .007), reported Dr. Gillison, who is now professor of thoracic/head and neck medical oncology at the University of Texas MD Anderson Cancer Center, Houston.
The vaccinated and unvaccinated groups did not differ significantly with respect to the combined prevalence of oral infection with 33 types of HPV that are not covered by vaccines.
When HPV vaccine uptake in the population in 2014 was considered, estimates suggested that vaccination was preventing only 17% of all vaccine-preventable oral HPV 16/18/6/11 infections in that year (25% in women and 7% in men).
Research on anogenital HPV infection, especially cervical HPV infection, suggests that most individuals will clear the infection on their own naturally, without any intervention, Dr. Gillison said. However, research has failed to identify good predictors of clearance or persistence.
“That’s why there is the current recommendation for universal vaccination of young boys and girls, because we don’t know how to distinguish someone who, like the overwhelming majority of individuals, is going to clear their infection with their own immune system, versus those who don’t have that capability and could progress to cancer,” she said.
Dr. Gillison disclosed that she has a consulting or advisory role with GlaxoSmithKline, Lilly, Bristol-Myers Squibb, AstraZeneca, Merck, and Celgene, and that she receives research funding (institutional) from Bristol-Myers Squibb, Kyowa Hakko Kirin, AstraZeneca, and Merck.