In the 1840’s, doctors in Italy made a keen observation: nuns did not get cervical cancer while married women did. This observation led scientists to question whether a sexually transmitted infection caused the disease. It also paved the way for decades of research, which ultimately led to the discovery of the responsible agent, human papillomavirus (HPV). Over the course of the last century, great strides have been made in our understanding of HPV and its transmission. These strides have led to the development of a preventive vaccine and generated much discussion as to who should receive it. At first it was only recommended for young women, but last week, the Centers for Disease Control (CDC) issued its vaccination schedule for 2012 and recommended for the first time that males get immunized against HPV.

Before we review the CDC’s recommendations, lets backtrack and discuss HPV in some more detail. HPV collectively refers to a group of related viruses that infect mucosal and epithelial tissues in humans. Most strains do not cause disease and are warded off by the immune system. Some can result in skin warts around the genitalia and papillomas (benign mucosal tissue growths) in the respiratory tract. A few strains cause infected cells to transform into cancerous cells and are responsible for causing cervical cancer, anal cancer, and oropharyngeal cancer (cancers of the oral cavity, tongue, and throat). HPV is transmitted through sexual contact and can infect the oral mucosa through oral sex. HPV infected individuals may remain asymptomatic; some are silent carriers and transmit the virus through sexual contact. This is how women with cervical cancer contract the virus from asymptomatic male sexual partners.

The first HPV vaccine was developed by Merck and approved by the Food and Drug Administration (FDA) in 2006. While the vaccine does not protect against all strains of HPV, it targets the two strains that cause the majority of HPV-related cancers. Up until recently, the CDC only recommended HPV vaccination in females as a means of preventing cervical cancer. However, last week the CDC’s Advisory Committee on Immunization Practices (ACIP) released its new vaccination schedule, which includes immunization against HPV for all males aged 11-12 years and follow up immunizations for those between the ages of 13 and 21. These new recommendations are published in last week’s edition of the Annals of Internal Medicine. ACIP also recommends that males between the ages of 22 and 26, who have sex with men, are immunocompromised, or test positive for HIV receive the vaccine. These new recommendations are based on the accumulation of evidence that immunization against HPV can prevent genital warts and cervical cancer. Given that males can harbor the virus and transmit it to female sexual partners, immunizing men could further contribute to the reductions in cervical cancer rates.

Interestingly, the CDC’s modified recommendation regarding HPV immunization come at a time when new data are emerging on the trends of HPV infection and HPV-related cancers, especially oropharyngeal cancer. A study published in the February 1st edition of the Journal of the American Medical Association (JAMA) this year, found that men were more likely than women to harbor HPV infection in the oral mucosa. It also confirmed a correlation between levels of sexual activity and HPV infection. A separate study from the United Kingdom, published last week in the journal Head and Neck examined the rates of HPV-associated oropharyngeal cancers over time. The investigators found that before the year 2000, only 40 percent of oropharyngeal cancers were associated with HPV, while after 2005, 70 percent of these cancers were found to be associated with HPV. The conclusions of this study need to be corroborated with additional research, but these results confirm that HPV-related oropharyngeal cancer is increasing and that greater attention needs to be given to preventing HPV infection in males.

Thus far the HPV vaccine has shown promise in terms of its potential to protect against cervical cancer. In theory, this promise also applies to oropharyngeal cancer. Given the higher rates of HPV in oral mucosa of males reported in last week’s study in JAMA, the CDC’s new decision to recommend immunization in males could have substantial impact on reducing transmission of this virus and possibly the rates of oropharyngeal cancer. However, rigorous clinical studies are needed to substantiate this notion.

References:
Advisory Committee on Immunization Practices. Recommended Adult Immunization Schedule, United States 2012. January 31, 2012. Annals of Internal Medicine.

Gillison ML, et al. Prevalence of Oral HPV Infection in the United States, 2009-2010. Journal of the American Medical Association. Electronic publication, January 26, 2012.

Mehanna M, et al. Prevalence of human papillomavirus in oropharyngeal and nonoropharyngeal head and neck cancer—systematic review and meta-analysis of trends by time and region. Head and Neck. Electronic publication, January 20, 2012.