Human papillomavirus (HPV) is found in human populations worldwide. Each HPV type has a special niche,or site, it prefers to infect. Thus, different HPV types cause different diseases ranging from common warts of the skin,to genital warts, cervical, vulvar and vaginal cancer, anal cancer, and head and neck (oropharyngeal) cancer.
HPV infection is the most common sexually transmitted infection in the world. Infection by high-riskHPV has a high risk for progression to cancer. Although high-riskHPV infection is best known as the cause of cervical cancer, HPV types 16 and 18 commonly cause cancers at other sites as well. Outside of the anogenital region, the most common HPV associated cancers occur in the oropharynx (approximately 50% of cancer cases in the oropharynx are caused by HPV infection). Notably, the prevalence of oral HPV is significantly higher in men than in women, and the rates of oropharyngeal cancer in men appears to be increasing.
The oropharynx comprises the mouth and throat, including the base of the tongue and the tonsils. Infection occurs as a result of oral to genital sexual contact when one of the partners has HPV infection. Normally, HPV infection is cleared rapidly by the body’s immune response, but when the immune system cannot clear the infection, the virus persists in the infected cells and can cause mutations that lead to tumor formation. The most common type of HPV-associated cancer by far is squamous cell carcinoma. Thus, all new cases of squamous cell carcinoma diagnosed from the oropharynx should be tested for the presence of HPV.
HPV vaccination is highly effective in preventing oral infection with HPV 16/18, thus significantly reducing the risk of oropharyngeal cancer, in addition to high levels of effectiveness in preventing HPV-related disease of the cervix, vulva, vagina, anus, and penis.
Barriers to Vaccination
Improving vaccination coverage is important in reducing the risk of cancer and disease causedby HPV. In comparison with other vaccinations recommended for adolescents such as tetanus, diphtheria, pertussis and meningococcal vaccine, HPV vaccination coverage is only slowly increasing and remains below Healthy People 2020 targets (see Call to Action). The effectiveness of current vaccine programs is heavily dependent on access and attitudes toward vaccination. Missed vaccinations often occur in the settingof socialstigma associated with HPV as a sexually transmitted infection. Often, healthcare providers or parents opt to delay vaccination until they believe a child is ‘about to be’ sexually active. This strategy is based upon denialand is strongly associated with a missed opportunity to protect the child from HPV infection before the onset of sexual activity. Even in countries with vaccine education, there are drastic differences in vaccination rates based on cultural beliefs. In addition, lack of universal health care programs, especially in developing countries, presents a significant barrier limiting rates of HPV vaccination.
How do we overcome these obstacles? Locally, social media campaigns, along with provider and parental education programs have had some success. But the most pressing global issue limiting vaccination is cost. Free or subsidized vaccination available to low income, high-risk individuals may be the most effective strategy.