New York Times (07.18.2013)
Study results indicate that the human papillomavirus (HPV) vaccine that prevents women from acquiring the strains of HPV that cause cervical cancer also seems to protect them from throat cancer caused by HPV infection acquired during oral sex. At present, HPV causes approximately 70 percent of oropharyngeal cancers, compared with 16 percent in the 1980s.
Researchers studied 5,840 sexually active 18–25-year-old Costa Rican women who had received either the HPV vaccine Cervarix or placebo. At the end of four years, each participant provided a mouthwash gargle sample that collected throat cells. Results showed that only one participant who had received the HPV vaccine was infected with the HPV-16 or HPV-18 viruses that cause cancer, while 15 women who had received placebo vaccine were infected.
Dr. Rolando Herrero, head of prevention for the World Health Organization’s International Agency for Research on Cancer and the lead author, listed the limitations of the study, including the absence of men from the study and the fact that participating women were given baseline tests to make sure they had no cervical infections but were not tested for throat or anal infections because the study’s initial focus was cervical cancer. Additionally, researchers collected only one oral sample, so they did not know if any participants had persistent infections; and some people clear HPV on their own, so only a small number might lead to cancer. Herrero also noted that four years was not long enough to know how many cancers would develop. Researchers would have to wait 20 years or more to know for sure, but ethical guidelines required that all participants get regular examinations and that their physicians destroy any suspicious lesions before they turn cancerous. Herrero surmised that men would get the same protection from an HPV vaccination as the women because the vaccine produces identical antibody levels in both sexes.
Dr. Marshall R. Posner, medical director for head and neck cancer at Mount Sinai Medical Center in New York, commented that the large discrepancy in infection rates between the control group and the vaccinated participants suggested the data were very reliable; however, he noted that no one knew the length of the vaccine’s protection or if re-vaccination was necessary.
The full report, “Reduced Prevalence of Oral Human Papillomavirus (HPV) 4 Years After Bivalent HPV Vaccination in a Randomized Clinical Trial in Costa Rica,” was published in the journal PLOS One (2013; doi:10.1371/journal.pone.0068329) .