Research finds evidence HPV vaccine is improving herd immunity

A study from researchers at The University of Texas MD Anderson Cancer Center found that the prevalence of the types of oral human papillomavirus (HPV) infections prevented by the HPV vaccine dropped by 37% over an eight-year period in unvaccinated U.S. men ages 18 to 59.

The investigators performed a study of oral HPV infection in the U.S. population in collaboration with the Center for Disease Control and Prevention (CDC) National Health and Nutrition Examination Survey. The team looked for evidence of herd protection against oral HPV infections in adults who had not received the HPV vaccine.

Herd protection, or herd immunity, occurs when a critical number of people have been vaccinated, making it harder for the virus to reach unvaccinated people. The authors attribute the improved herd protection in males to the increasing numbers of U.S. women receiving the HPV vaccine.

“The HPV vaccine is not approved for prevention of oral HPV infections that elevate risk of mouth and throat cancers because of a lack of clinical trials,” says corresponding author Maura Gillison, M.D., Ph.D., professor of Thoracic/Head & Neck Medical Oncology and co-leader of the HPV-Related Cancers Moon Shot®. “It is critical to obtain high-level evidence of the vaccine’s potential to reverse an ongoing epidemic of HPV-positive oral cancers among men in the U.S. and worldwide.”

The study, published in JAMA, is a follow-up to work Gillison and team published in Journal of Clinical Oncology in 2017, which found that the HPV vaccine may reduce the rate of oral HPV infections in young adults by as much as 88%.

Throat cancers rising in men

HPV-related oropharyngeal cancers have been on the rise in men in recent years. In many cases, the virus does not cause symptoms and the cancer doesn’t appear until many years after the initial infection. However, the HPV vaccine can prevent many oropharyngeal, cervical, anal and penile cancers.

“Cervical cancer rates have been declining in the U.S. for decades because of a successful screening program,” Gillison says. “There is no analogous screening program for HPV-positive oral cancers. The vaccine is our current best hope for prevention. Our data underscore the importance of ongoing efforts to increase HPV vaccination rates in the U.S. The entire population will benefit.”

The HPV vaccine protects against several of the most-common cancer-causing forms of the virus. The study compared four types of the virus covered by the HPV vaccine and 33 types of the virus not covered by the vaccine. Results showed that only vaccine-type oral HPV infections declined; infections caused by types of the virus not covered by the vaccine remained unchanged.

HPV infection rates also remained unchanged during the survey period in women, which the authors suggest could be due to low statistical power in the study because of the low rates of oral HPV infections in women. Use of self-reported vaccination information was a limitation of the study.

This study was supported in part by NIDCR grant R01DE023175 and the Intramural Research Program of the National Cancer Institute. Gillison is a Cancer Prevention and Research Institute of Texas (CPRIT) Scholar and reported consulting disclosures. MD Anderson co-author on the study was Weihong Xiao, M.D., Ph.D. Gillison also notes the contribution of NCI collaborators Anil Chaturvedi, Ph.D., and Barry Graubard, Ph.D. See the full list of co-authors and disclosures on the paper.