Gray P, et al. - In 33 Finnish communities, researchers examined vaccinated and unvaccinated subgroups of 1992-1994 birth cohorts with differing human papillomavirus (HPV) acquisition risks in order to determine the occurrence of HPV types up to 9 years post-implementation of HPV vaccination. Three arms were defined: Arm A (gender-neutral HPV16/18 vaccination), Arm B (girls-only HPV16/18 vaccination and hepatitis B-virus (HBV) vaccination of boys), and Arm C (gender-neutral HBV vaccination). Based on Chlamydia trachomatis positivity and negativity, Arms A/B vs C were assessed for HPV prevalence ratios (PR) and defined as Chlamydia trachomatis positives (core-group), and negatives (general population minus core group). They noted that there was no significant difference between the core-group and non-core group with respect to vaccine-protected HPV type PRs at both visits. Overall, somewhat increased occurrence of HPV51 was observed among the vaccinated 18-year-olds, however, only the core-group demonstrated increased HPV52 occurrence. Findings revealed higher HPV51/52 PRs in the core-group among the non-HPV vaccinated 18-year-olds. Overall, early tendencies for HPV type-replacement could be identified via monitoring of the sexual risk-taking core-group.