Incidence and Predictors of Human Papillomavirus-6,-11,-16, and-18 Infection in Young Norwegian Women

Background: Natural history data on human papillomavirus (HPV) incidence and its risk factors have not been reported on from young women in Norway. We report on incidence and predictors of HPV-6, 11, 16, and 18; 6 or 11; 16 or 18; or all 4. Methods: A 48-month prospective study enrolled 898 women aged 16 to 24 between 1998 and 2000. HPV DNA polymerase chain reaction testing of genital tract specimens was performed and risk data collected every 6 months and HPV serology and genital Chlamydia trachomatis testing performed every 12 months. Cumulative incidence was estimated using the Kaplan-Meier method and covariates evaluated in Cox models. Results: Among the women who were HPV DNA-and serology-negative at entry, 48-month cumulative incidences (95% confidence interval) were as follows: HPV-6: 20.0% (17.1-23.4), HPV-11: 2.2% (1.3-3.5), HPV-16: 25.0% (21.7-28.8), HPV-18: 13.6% (11.3-16.4), HPV-6 or -11: 21.5% (18.5-25.0), HPV-16 or -18: 30.4% (26.7-34.5), and HPV-6, -11, -16, or -18: 37.8% (33.6-42.3). Younger age at first intercourse, being single, having no regular partner, reporting new partners, and genital C. trachomatis infection were independent risk factors of incident HPV. Conclusions: Proxies measuring new partnerships and genital C. trachomatis infection predicted incident HPV-6, -11, -16, or -18. Incidence of HPV-6, -11, -16, or -18 in young Norwegian women is high, with more than one-third becoming infected over 48 months.