Not every case of cervical cancer is caused by viral infection, and the human papillomavirus comes in a number of tumor-inducing strains. Gardasil protects against:
- HPV16, and
- HPV 18,
but cervical cancer can also be caused by infections with the HPV33, HPV45, HPV52, HPV53, and HPV62 as well as other strains of the virus that are not covered by the vaccine. Moreover, women can be infected with more than one strain of the virus at the same time.
What do cervical cancer statistics tell us about how many women might get some real level of protection from Gardasil?
Outside the United States, particularly in the Caribbean and in Africa, HPV45 is the most common strain of human papillomavirus causing cervical cancer, and even in the United States, almost half of women infected with HPV are not infected with HPV6, HPV11, HPV16, or HPV18.
There is a reason the vaccine makers concentrated on these strains, however. The kinds of human papillomavirus that infect women outside North America and that infect some women even in the United States tend to cause a "warty" tumor that can be located and excised. HPV18, in particular, tends to cause a highly invasive tumor that has to be caught early for treatment to be successful.
Gardasil, then, is not designed to prevent all cervical cancer, but it is designed to prevent the most invasive forms of the cancer. All sexually active women, particularly women on the Pill and women who smoke, still need to follow their regular schedule of Pap smears and cervical exam, and all women can still benefit from simple, diet-based natural methods of preventing cervical cancer.
Sutton BC, Allen RA, Moore WE, Dunn ST.Distribution of human papillomavirus genotypes in invasive squamous carcinoma of the vulva. Mod Pathol. 2008 Mar;21(3):345-54. Epub 2008 Jan 11.