Ontario data examined by Queen’s, McGill researchers
The HPV vaccine, which protects against four types of HPV shown to cause cervical cancer and anogenital warts, is offered free through school-based programs to young girls across Canada. Despite the fact the vaccine is free, vaccine rates are lower than expected in a number of regions, in part because parents perceive their daughter’s level of sexual activity as low at young ages.
“We observed a large and significant reduction in cervical dysplasia, a precursor to cervical cancer, in girls as young as 14-17 years,” say Leah Smith and Linda Lévesque, researchers with the Institute for Clinical Evaluative Sciences (ICES) at Queen’s University.
McGill professors Jay Kaufman, from the Department of Epidemiology, Biostatistics and Occupational Health (EBOH), and Erin Strumpf, from EBOH and the Department of Economics, co-authored the study.
The study, published in the journal Pediatrics, also found the vaccine is starting to decrease genital warts in this population.
“The fact that these benefits were observed in such a young age group strengthens current recommendations that vaccination should not be delayed,” says Dr. Smith, lead author on the study and a former McGill PhD student.
This study followed 260,493 girls, half of whom were eligible for Ontario’s publicly funded Grade 8 HPV vaccination program in its first two years (2007/08 and 2008/09).
Researchers found that among the 2,436 cases of cervical dysplasia documented between Grades 10 to 12, 44 percent fewer cases occurred in eligible girls who received the vaccine. The research showed that one case of cervical dysplasia was prevented for every 175 eligible girls vaccinated.
“Although the vast majority of cases prevented by the vaccine would not have progressed to cervical cancer, given the burden of cervical dysplasia on the emotional and physical well-being of girls as well as on the health-care system, these early reductions are nevertheless of great importance,” says Dr. Lévesque.
Funding for the research was provided by the Canadian Institutes of Health Research, the Institute for Clinical Evaluative Sciences, the Fonds de la Recherche du Québec–Santé, the Canada Research Chairs program, the Canadian Cancer Society Research Institute, and the Canada Foundation for Innovation.
“The Early Benefits of Human Papillomavirus Vaccination on Cervical Dysplasia and Anogenital Warts,” Leah M. Smith et al. Pediatrics, Volume 135, number 5, May 2015. doi: 10.1542/peds.2014-2961
April 30, 2015