Induced abortion rates among women vaccinated against human papillomavirus: Registry-based follow-up of a community-randomized trial.

Abstract

Concerns have been raised that human papillomavirus (HPV)-vaccination programs may alter risk perceptions and increase risk-taking sexual behavior among adolescents. This study aimed to assess induced abortion rates (as a potential indicator of such behavior) between vaccinated and unvaccinated individuals. This longitudinal, cluster-randomized cohort study included 6200 HPV-vaccinated women born in 1992-1993 who participated in a 2007 launched HPV-vaccination trial in Finland, and 19,473 unvaccinated women born in 1990-1991 from the same communities. Registry data from a 12-year follow-up period (between 2007 and 2020, depending on the group) up to the age of 28 years was obtained from The Finnish Register on Induced Abortions. Incidence rate of induced abortions per 10,000 person-years was significantly lower among HPV-vaccinated (145.6(95 %CI 137.1,154.5)) compared to unvaccinated individuals (161.4(95 %CI 156.4,166.7)). HPV-vaccinated individuals induced abortions in earlier gestational weeks (p = 0.049). Up to four-years post sexual health education given at HPV vaccination visits, induced abortion rates were significantly lower among individuals aged 15-19 (33.7(95 %CI 29.8,38.2)) than age-aligned unvaccinated controls (42.4(95 %CI 38.9,44.1)). HPV-vaccinated had lower induced abortion rates than unvaccinated individuals. When further developing HPV-vaccination programs, simultaneous sexual health education should be considered to comprehensively improve the reproductive health of adolescents.