Few cancers have a definite cause. And yet that is the case with cervical cancer, the second leading form of cancer among women worldwide, especially in young adults. The mortality rate associated with this type of cancer has dropped dramatically in developed countries since the use of Pap tests (a microscopic analysis of cervical cells) became widespread. The test allows us to detect the presence of precancerous cells and therefore to begin treatment before the cancer really sets in. Screening is not perfect, however: 1,350 Canadian women were diagnosed with cervical cancer in 2006 and 309 died from it.
Human papillomavirus (HPV) is transmitted through skin contact and is the most common sexually transmitted infection. In fact, most sexually active men and women will be exposed to one or another of the virus’ many strains at some point in their life. Most of these infections will go unnoticed and will spontaneously resorb within 24 months. Some infections persist, however. This is how almost all cervical and vaginal cancers, and a significant proportion of cancers of the vulva, anus and mouth, are linked to a few HPV strains. Some strains of HPV also cause condylomas, commonly called genital warts.
Vaccination therefore aims to prevent HPV infections, which are difficult to avoid in sexually active adults. Even systematically wearing a condom only offers limited protection. Vaccination may be the only way to prevent infection.
In Canada, the HPV vaccine is indicated for 9- to 26-year-old girls and young women. It protects against two HPV strains responsible for uterine cancer and two strains responsible for condylomas and abnormalities detected with Pap tests. The vaccine is associated with very few adverse effects, the most common being pain at the injection site. Fever and flu-like symptoms may also occur. Studies suggest that even young women who are already sexually active may benefit from the vaccine, since it is unlikely that they have already been infected by the four strains contained in the vaccine. Some experts believe that boys and young men should also be vaccinated in order to slow the transmission of anal cancer, which is uncommon but serious.
It remains essential for women’s sexual health that they undergo regular medical checkups and practice safe sex. The vaccine should never take the place of Pap test screenings.