The study comes following concern from some parents that the publicly funded vaccination program could encourage early sexual activity and unprotected sex.
HPV is a common, sexually transmitted infection that often resolves naturally without intervention. But if left untreated, persistent infection with high-risk types of the virus can cause precancerous lesions that may progress to cervical, anal, or reproductive tract cancers.
The vaccination program was introduced in schools in 2008 for girls in grades 6 and 9, and for girls in grade 6 after 2011.
“This large, prospective study over 10 years, conducted both before and after HPV vaccine implementation, shows that adolescent young women have not changed their sexual health practices since the introduction of the vaccine program,” said Dr. Gina Ogilvie, lead study author, Canada Research Chair in Global Control of HPV-Related Disease and Cancer, and assistant director at the Women’s Health Research Institute at BC Women’s Hospital + Health Centre.
Researchers examined data from the BC Adolescent Health Survey, a population-based survey of students in Grades 7 to 12 conducted every five years. The data came from surveys conducted in 2003, 2008 and 2013, representing approximately 300,000 girls in BC public schools.
The study found that the percentage of girls who reported ever having sex decreased from 21.3 per cent in 2003 to 20.6 per cent in 2008 and further dropped to 18.3 per cent in 2013.
The percentage of girls having intercourse before age 14 also decreased between 2008 and 2013, and condom use increased from 65 per cent in 2003 to 68.9 per cent in 2013.
“What we have seen over the past 10 years is that young people are making healthier choices around sexual behaviours,” said Elizabeth Saewyc, senior study author and a professor at the UBC school of nursing.
“The knowledge and information about sexual health and the availability of the HPV vaccine to help prevent cancer has not changed things for the worse.”
While the results of this paper are specific to girls in BC, Ogilvie said they align with similar research around the world.
“These findings are consistent with studies in Scandinavia and smaller clinic-based studies in the US, confirming that adolescent women do not make poorer sexual health choices after the HPV vaccine,” said Ogilvie, who is also a professor at UBC’s School of Population and Public Health.
It’s estimated that more than 70 per cent of sexually active Canadian women and men will have at least one HPV infection in their lifetime.
A similar vaccine for boys was introduced on a broad scale only recently. Researchers say future studies should include sexual behaviour trends among boys and girls.
The study’s authors included Monika Naus, Medical Director of the Communicable Diseases & Immunization Service at BCCDC. It was funded by the Canadian Institute of Health Research (CIHR).