HPV Vaccine Shown to Protect Against Oral Form of InfectionJul 24, 2013
Researchers from the National Cancer Institute (NCI) and colleagues have found that the human papillomavirus (HPV) vaccine protects women from a form of the virus that causes oral infection as well as cervical infection. Oral infection with HPV increases the risk for throat cancer.
HPV is a group of more than 150 types of viruses. HPV-16 is the type most often linked to throat cancer. The 2 HPV vaccines available – Cervarix and Gardasil – prevent infections with both HPV-16 and HPV-18, the strains that are responsible for most cases of cervical cancer.
The study, published online July 17, 2013 in PLOS One, was part of the NCI Costa Rica Vaccine Trial. The trial assigned more than 7,000 women ages 18 to 25 to receive either the Cervarix vaccine or a vaccine against the hepatitis A virus, as a comparison. Four years later, researchers found only 16 of the women had contracted an oral HPV infection – 1 in the HPV vaccine group and 15 in the comparison group. This calculates to a 93% reduction in the rate of HPV infection in women who received the vaccine compared to women who did not.
According to Debbie Saslow, PhD, American Cancer Society director of breast and gynecologic cancer, this is preliminary, but very promising evidence that HPV vaccines might prevent most oral HPV infections, and may also have a significant impact on the prevalence of throat cancer.
Saslow said, “HPV, and particularly HPV-16, is responsible for an increasing proportion of throat cancers. If the vaccine does indeed prevent HPV-associated throat cancers, then it will have a significant impact. HPV-16 is now responsible for over half of all throat cancers, with some estimates at around 70%.”
The data from the new study would still be considered preliminary, according to Saslow, because of the small number of oral HPV infections even in the control group, and the relatively short length of time the women were followed. In addition, the study included only women, while more men get HPV-linked throat cancer.
Still, there is no reason to believe that the vaccine would be any less effective in males than females, according to Saslow. “Throat cancer affects 3 or 4 men for every 1 woman, so it is likely that vaccination of males will have a significant impact on male oral HPV infection and throat cancer,” she said.
The Centers for Disease Control and Prevention (CDC) recommends the vaccine for boys and girls ages 11 and 12, and for boys and young men ages 13 through 21 and girls and young women ages 13 to 26 who have not already had all 3 shots. Vaccinations may also be given to children as young as 9 and to men between the ages of 22 and 26.
The American Cancer Society does not yet have recommendations for vaccination of boys, but recommends girls get the vaccine at ages 11 and 12. The vaccine is also recommended for girls ages 13 to 18 who have not already had all 3 shots. To work best, the HPV vaccine should be given before a person has had any type of sexual contact with another person.
Most people with HPV infections of the mouth and throat have no symptoms, and only a very small percentage go on to develop throat cancer. The risk of oral HPV infection is linked to certain sexual behaviors, such as open mouth kissing and oral sex. Smoking also increases the risk of oral HPV infection. In people without HPV infection, the main risk factors for throat cancer are alcohol and smoking.
Reduced Prevalence of Oral Human Papillomavirus (HPV) 4 Years after Bivalent HPV Vaccination in a Randomized Clinical Trial in Costa Rica. Published online July 17, 2013 in PLOS One. First author: Rolando Herrero, PhD, International Agency for Research on Cancer, Lyon, France.