study finds no evidence of riskier sex after hpv vaccine introduced
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a girl winces as she is injected with the hpv vaccine.
john amis
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b.c. public health experts say they now have evidence to refute concerns of people who worried the hpv vaccine would lead to promiscuity among youth.
when the vaccine against the cancer-causing, sexually transmitted human papillomavirus became publicly funded for grade 6 and grade 9 girls in 2008, some religious leaders and parents said it was akin to condoning sexual activity and would lead youth to have sex earlier, with more partners and without protection. since 2011, it is freely available only to girls in grade 6.
but a new b.c. study, published in the canadian medical association journal, found that after the vaccine was introduced, girls were less likely to have intercourse before the age of 14, less likely to drink alcohol and less likely to take drugs. girls in grades 7 to 12 also used contraception and condoms more often, and reported fewer pregnancies.
the lead author, dr. gina ogilvie of the b.c. centre for disease control, credits improved sex education and awareness for the changes.
ogilvie and her co-authors used b.c.’s adolescent health survey, done every five years, to detect changes in sexual behaviours of girls before and after hpv vaccinations were introduced into schools. data from the 2003, 2008 and 2013 surveys were analyzed. the study is based on responses from about 300,000 girls who identified as heterosexual and completed the anonymous questionnaire designed to spot trends in the physical and emotional health of students.
“it’s not that kids are becoming more conservative,” ogilvie said of the findings. “it’s that they are more informed about the consequences of their decisions and they have more autonomy to make choices about their bodies.
“parents told us in surveys that they were concerned their children would make poor sexual health choices if they were vaccinated against hpv, but children know that this is only one type of sexually transmissible infection, among others like chlamydia, gonorrhea, and syphilis,” she said.
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the proportion of girls in grades 7 through 12 who reported having had intercourse steadily decreased. it dropped to 18.3 per cent in 2013, from 21.3 per cent in 2003. the proportion engaging in intercourse before the age of 14 dropped to 10.2 per cent, from 14.3 in 2003.
the study concludes that girls were “significantly less likely to report ever having sex after the introduction of the hpv vaccination.”
ogilvie said the study confirms what research around the world is showing.
she acknowledges the study is based on a survey and does not prove a cause-and-effect relationship between hpv vaccination and sexual behaviours. the study does, however, show there’s been a trend toward safer sex practices starting before the hpv vaccine was introduced.
hpv is the most common sexually transmitted infection in the world. most infections clear up on their own. but some strains of hpv can cause precancerous lesions that can lead to cervical and other reproductive tract cancers, anal cancer and oral cancer.
in 2013, about 69 per cent of girls received the vaccinations, slightly more than the proportion who got it earlier but not yet close to the goal of 90 per cent envisioned by public health experts. public coverage of vaccination for boys is also available in b.c. and in future studies based on the youth survey, experts will look at data from boys.
there are various vaccines that protect against two hpv strains that cause 70 per cent of cervical cancers. gardasil-9 also reduces the risk of other types of hpv that cause genital warts and other cancers besides cervical.
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