A new study on the health impacts of Alberta’s human papillomavirus (HPV) vaccination program finds it has cut the risk of cervical cancer in young women by 50 per cent since its inception in 2008, a result which makes Alberta’s HPV program a success in the eyes of health experts.
“Eight years after a school-based HPV vaccination was initiated in Alberta, 3-dose HPV vaccination has demonstrated early benefits,” say the study’s authors, “particularly against high-grade cervical abnormalities, which are more likely to progress to cervical cancer.”
Researchers looked at health records for 10,204 young women born between 1994 and 1997, representing the first cohort of age-eligible participants in the province’s HPV vaccination program. Of that group, 56 per cent were unvaccinated and 44 per cent had at least one dose of HPV vaccine before cervical cancer screening between 2006 and 2015. The researchers found that among the unvaccinated women, 16.1 per cent had cervical abnormalities compared to 11.8 per cent from the fully vaccinated group.
“That’s a very significant finding,” says Dr. Huiming Yang, Medical Officer of Health and Medical Director, Screening Programs with Alberta Health Services in Calgary. “It was what we hoped for, because the clinical trial data years ago basically showed similar results, and now we basically have proof that this worked with a real population.”
HPV is the most commonly contracted sexually transmitted infection, with an estimated 75 per cent of sexually active Canadian males and females likely to contract an HPV infection at some point during their lifetime. A leading cause of cervical cancer in women, HPV can also result in other genital and oral cancers in both men and women. The Canadian Cancer Society reports that most HPV infections (about 70 per cent) go away without treatment within one to two years but that persistent infection can cause precancerous abnormalities, detectable through screening processes such as the Pap test.
Since their inception in the mid-2000s, HPV vaccines such as Gardasil have been proven effective in preventing infection from certain strains of the HPV virus, but the Alberta study marks the first in North America to look into the efficacy of a school-based HPV vaccination program. Alberta opened its program in 2008 to female students in grade five (ages 10 and 11) and then added a catch-up program in 2009 for female students in grade nine (ages 14 and 15), followed by the addition of male students in 2014.
Alberta’s is a three-dose program, meaning that students normally receive a total of three doses of the vaccine over the course of the school year, but the study, published this month in the Canadian Medical Association Journal, found that those students who only received two doses had higher rates of cervical abnormalities, arguing against the efficacy of the two-dose approach, say the study’s authors.
Currently, Canada’s National Advisory Committee on Immunization has recommended a two-dose HPV vaccination schedule, a position adopted by other regions such as the United Kingdom where in 2014 health officials scaled down from a three-dose to a two-dose program.