A step closer to eliminating cervical cancer by 2040
Cervical cancer could be eliminated worldwide by 2040, according to a study published last week. The key is to immunize young girls with the human papillomavirus (HPV) vaccine. That huge task may have just gotten easier thanks to a study published Monday in the online edition of the journal Cancer.
The current U.S. recommendation is that teen girls receive two doses of the HPV vaccine. Dr. Ana M. Rodriguez at the University of Texas Medical Branch at Galveston, and colleagues looked at the records of 133,082 females ages nine to 26 years. For girls under 15 or older than 20 years, one dose of HPV vaccine was equally effective as two or three doses. For those ages 15 to 19 years, one dose of HPV vaccine was as good if not better against preclinical cervical disease.
Human papillomavirus is the most common sexually transmitted infection. There are many different strains of HPV. Two of them (HPV16 and HPV18) can cause abnormal lesions known as precancers which are precursors to cervical cancer. HPV16 and HPV18 account for about 70 per cent all cases of cervical cancer worldwide. A Cochrane review that looked at 26 studies showed that vaccination against the two strains substantially reduced the risk of cervical precancers.
The current study is important in that it adds to existing evidence that one dose is adequate to protect against HPV strains that cause cervical cancer.
An editorial that accompanied the study says there's a worldwide shortage of HPV vaccine. The shortage is having an effect on the planned scale-up of mass immunization across the globe, which is a big part of the World Health Organization's call to eliminate of cervical cancer as a public health problem.
That means vaccinating 90 per cent of all girls by the age of 15 years by the year 2030. In general, it's a challenge to get adolescents to complete a series of vaccinations. Going to one dose of HPV vaccine would make that job easier while extending current supplies much further.
Between 2007 and 2010, all provinces and territories in Canada implemented publicly funded routine HPV immunization programs for girls with a vaccine against serotypes 6, 11, 16 and 18. There are three HPV vaccines approved in Canada that differ somewhat in formulation and strain coverage. The Canadian Pediatric Society recommendations can be found here.
Generally speaking, HPV vaccination is recommended for all young men and women. Most provinces and territories provide coverage for students in Grades 6 or 7 through school vaccination programs. But the rules are inconsistent across Canada. Ontario offers a catch-up program for the vaccine at no cost to any female who is still enrolled in high school. The catch-up program in B.C. is available for females up to age 26.
We know from studies that HPV vaccine prevents precancerous lesions of the cervix. It takes years for an HPV infection to cause cancer. Thus, it will take years to prove conclusively that widespread HPV vaccination eliminates cervical cancer. The upfront cost of mass vaccination is expensive. With growing rates of vaccine hesitancy, there are fears that scepticism about HPV vaccine could stall efforts to eliminate the disease.
Despite these challenges, the goal of eliminating cervical cancer by the year 2040 is achievable. As a physician, I have diagnosed the disease and have seen patients with stage 4 cancer who cannot be cured. We have a vaccine that can make the latter increasingly unlikely.