Hence, HPV vaccinees were less likely to have an unprotected sexual debut than were non-vaccinees. The difference SCH772984 relative to non-vaccinees was large and highly significant for organized vaccinees (adjusted odds ratio (95%CI): 0.27 (0.15; 0.48)), while it was less pronounced for opportunistic vaccinees (0.69 (0.52; 0.93)).
To our knowledge, this is the largest study to date addressing the association between HPV vaccination and sexual behaviour in several countries. Since events that happen prior to HPV vaccination cannot be related to the vaccination, we investigated sexual behaviour occurring subsequent to vaccination. This approach addresses the issue of risk compensation  more precisely than analyses that do not take the sequence of vaccination and sexual behaviour into account. Our analyses show that women vaccinated prior to sexual debut did not differ from unvaccinated women in terms of age at first intercourse or subsequent number of sexual partners, and that they had a lower frequency of unprotected sex at first intercourse. This indicates that the experience of being vaccinated against HPV does not lead to an increase in sexual risk taking behaviour. Hence, we found no evidence of risk compensation among HPV vaccinees.
We addressed sexual risk compensation separately for opportunistic and organized catch-up vaccination. Further studies are needed to investigate whether the findings of this study also apply to organized GW572016 vaccination of prepubescent girls. Opportunistic vaccination has been shown to be associated with high socioeconomic status , which is also likely to apply to our study since most opportunistic vaccinees had to pay the entire vaccine cost. In contrast, organized catch-up vaccination was free of charge
and initiated by individual invitation, and may hence have been less influenced by socioeconomic status. We did not find evidence for sexual risk compensation in any of the vaccination all settings investigated, which indicates that socioeconomic status did not strongly influence our assessments of sexual behaviour by vaccination status. Note that we adjusted all analyses for educational level, a proxy for socioeconomic status that may be associated with sexual behaviour  and . Contrary to the hypothesis of risk compensation, some of our analyses showed that HPV vaccinees had a less risky sexual behaviour subsequent to vaccination than did non-vaccinees. It is conceivable that individuals with a greater awareness of sexual health are more likely to get the HPV vaccine, or that the event of HPV vaccination increases individual awareness of sexual health. Individuals who seek vaccination could also be generally more risk averse. Previous studies also observed that HPV vaccinees do not have a more risky sexual behaviour profile than do non-vaccinees.