By analyzing data on both early-stage and late-stage anal and head and neck cancers, researchers have found that the rates of the early-stage cancers increased precipitously between 1978 and 2007, before the introduction of a vaccine for human papilloma virus (HPV). HPV infects tissues of the mucus membranes, such as the vagina, anus, and throat, and can lead to cancers in those three areas in individuals who cannot clear the infection. Two vaccines for HPV are currently on the market: Gardisil made by Merck and Cervarix produced by GlaxoSmithKline.

The study looked at government databases that tracked HPV-related cancers before the vaccine was introduced, for the last 30 years. Through the course of the period studied, researchers saw an increase in early stage cervical, vaginal, penile, anal, and head and neck cancers. According to the U.S. Centers for Disease Control and Prevention (CDC), there are 27,900 of these cancers in the U.S. each year, out of which 21,000 are believed to be preventable by vaccination against HPV. The trends were seen in all races, ages, and sexes through the time period examined. The researchers did note that in the 30-year window, early-stage cervical cancer rates increased, while late-stage ones decreased, a switch attributed to increased prevalence of screening.

The researchers point out that this research will set up a good starting point to determine the effectiveness of the HPV vaccine in preventing many types of cancers. Although the issue of the HPV vaccine has been contentious in the U.S. and use has been low, with less than one-third of teens receiving it, the vaccine does work in preventing infection of many strains of HPV. Early data from Australia, where HVP vaccination adoption is almost universal, indicates that there has been a sharp decline in the number of diagnosed genital warts, a symptom of HPV.

It will take years to determine the cancer incidence after vaccination programs because it can take over a decade for cancer to develop after infection. Governments are closely tracking the generation of teenagers who make up the first wave of vaccinated young adults.

Kurdgelashvili G, Dores G. M., Srour S. A., Chaturvedi A. K., Huycke M. M. and Devesa S. S. Incidence of potentially human papillomavirus-related neoplasms in the United States, 1978 to 2007. Cancer. 2013; 10.1002/cncr.27989. Accessed May 10, 2013.