Some fear that HPV vaccination may lead to an increase in unfavourable sexual health outcomes, based on the theory of risk compensation suggesting that the relative assurance of the protection from vaccination could be associated with an increase in risky sexual behaviours. Our study aimed to test whether receiving an additional dose of Q-HPV vaccine between the ages of 13 and 15, five years after the initial dose was received, would lead to more sexual activity and more risky sexual activity over a year, among teenage girls vaccinated in Quebec, Canada.
We analyzed data collected as part of an ongoing randomized trial, ICI-VPH, investigating the role of a booster dose of HPV vaccine. All participants received 2 doses of Q-HPV vaccine in fourth grade. The intervention group received an additional dose 60 months after their first one; the control group did not receive a vaccine booster dose. Girls included in the present analysis were those who had no sexual experience at the time of the randomization and who responded to the follow-up questionnaire one year later. The main outcome was the occurrence of the first sexual experience in the year following randomization. Secondary outcomes included: lifetime number of sexual partners, condom use, STIs and pregnancy.
Of 1581 girls, 798 (50.5%) received an additional Q-HPV vaccine dose and 783 (49.5%) did not. At the time of randomization, groups showed similar characteristics: the mean age was 14.8 years, 70.5% self-identified as French Canadian only, 91.3% were born in Canada, 12.0% were using hormonal contraception and 4.5% were smokers. In the year following randomization, similar proportions of participants initiated sexual activity (17.2% vs 19.9%; p-value 0.26); initiated intercourse (14.9% vs 16.4%; p-value 0.24); and used condoms (67.5% versus 63.4%; p-value 0.57). Only 2 participants reported an STI (one in each study group), and one reported a pregnancy (in the control group). In multivariate analysis, identifying as French Canadian only (OR 1.5; 95% CI: 1.1-2.0), tobacco smoking (OR 3.0; 95% CI: 1.8-5.1) and hormonal contraception use (OR 2.4; 95% CI: 1.7-3.4) were associated with sexual activity initiation.
We did not observe an increase in sexual activity, risky sexual behaviours or unfavourable sexual health outcomes in adolescent girls who received an additional dose of HPV vaccine between 13 and 15 years of age.