The human papillomavirus vaccine (HPV) is offered to girls before they hit their teens to prevent the spread of the STI, which can – in some cases – cause cervical cancer, genital warts, and other cancers.

Studies so far have shown that these national vaccination programs have proven to be a remarkable success. Yet, some people are concerned that they may be having another effect. That is, they might encourage teenage girls to be more sexually promiscuous and engage in riskier sexual behaviors. 

A study recently published in the Canadian Medical Association Journal (CMAJ) has shown that these fears are completely unfounded. In fact, if anything, the sexual behaviors of teenage girls have become quite a bit safer since the introduction of the vaccination program – at least in Canada. 

The Canadian province of British Columbia introduced a publicly funded routine HPV vaccination program in 2008 for girls in grades 6 (10 to 11 years old) and 9 (13 and 14 years old). In its very first year, take-up rates were 61.8 percent among those in grade 6 and 62.1 percent among those in grade 9. Two years later and rates had increased to 68.8 percent among girls in grade 6. By this point, it was no longer available for girls in grade 9.

To study the effects of the program on teenage sexual behavior, researchers from the University of British Columbia examined data from the 2003, 2008, and 2013 BC Adolescent Health Survey, a comprehensive population-based questionnaire taken once every five years by students in grades 7 to 12 (11 to 17 years old). Students were asked (anonymously) whether or not they had ever had sex and further questions on their sexual behavior, like whether they took oral contraception and how many sexual partners they had had. 

The responses of 298,265 girls were included in the study, all of whom described their sexuality as either heterosexual, unsure, questioning, or without attractions. (Girls identifying as lesbian or bisexual will be included in a separate study.) Only those in the final survey (2013) would have been offered the HPV vaccine.

So, what did the researchers find? First, the number of girls self-reporting being sexually active declined. The number of girls who reported ever having had sex was 21.3 percent in 2003. This dropped to 20.6 percent in 2008 and to 18.3 percent in 2013. There were also fewer girls having sex before age 14. 

Not only were the younger cohorts less sexually active, but those that were having sex appear to be doing so more safely. The use of condoms and oral contraception has increased over time, from 65.6 percent (2003) to 68.9 (2013) in the case of the former. The number of teenage girls on the birth control pill increased by 9.4 percent between the first and second survey.

The researchers also found that pregnancy rates declined dramatically (42 percent) between 2003 and 2013, while there was no significant change in the number of sexual partners reported. 

As the study authors explain, these results seem to mirror global trends towards safer sex practices, even in countries without a state-funded vaccination program for HPV.

It is, therefore, hard to tell whether or not the safer sexual behaviors are the result of the vaccine, improved sexual education in schools, better access to information about sex (read: the Internet), or something else altogether (or perhaps a combination of all the above). Future studies will hopefully provide more clarification as the team intend to add a self-reported question on HPV vaccination status in future surveys.