Occurrence of vaccine and non-vaccine human papillomavirus types in adolescent Finnish females 4 years post-vaccination.

Control of human papillomavirus (HPV)-related cancers by inclusion of HPV vaccination into national vaccination programmes is likely. One open question is replacement of the vaccine types with other high-risk (hr) HPV types in the vaccination era. We studied occurrence of HPV types in adolescent females participating in a population-based vaccination trial. A total of 4,808 16- to 17-year-old females from Finland were enrolled in the 1:1 randomized phase III (PATRICIA) trial of the efficacy of vaccination with the AS04-adjuvanted HPV-16/18 virus-like particle vaccine as compared to hepatitis A virus (HAV) vaccine. HPV infection was assessed from cervical samples taken every 6 months for 4 years post-vaccination by polymerase chain reaction (PCR) for genital oncogenic HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 58, 59, 66, 68, and 73 as well as low-risk types HPV-6 and HPV-11. The HPV-16/18 vaccine coverage ranged between 1 and 22% by age-cohort and study community. Odds ratios (ORs) for infections with different HPV types in baseline PCR negative HPV-16/18 vs. HAV vaccinated women, and Poisson regression derived HPV incidence rate ratios (IRRs) in baseline positive vs. negative women were calculated. The OR and IRR estimates for acquisition of any genital HPV types showed no excess risk neither in baseline HPV DNA-negative HPV-16/18-vaccinated women compared to baseline HPV DNA-negative HAV vaccinated women nor in HPV-16/18-vaccinated baseline HPV-16/18-positive women compared to baseline HPV-16/18-negative women. In the HAV-vaccinated, baseline HPV-18-positive women showed an increased risk of acquiring other clade A7 HPV types (39, 45, 59, 68) (IRR 1.8, 95% confidence interval = 1.01.-3.1). We found no increased occurrence of non-vaccine HPV types suggestive of type-replacement 1-4 years post-vaccination among HPV-16/18-vaccinated Finnish adolescents.