Time trends in incidence and prevalence of human papillomavirus type 6, 11 and 16 infections in Finland.

Human papillomavirus (HPV) type 16 is the major cause of cervical carcinoma, the incidence of which is decreasing in western countries. In Finland the incidence is, however, increasing in women aged <40 years, but possible underlying changes in HPV-16 epidemiology are unknown. To assess incidence trends of HPV infections, paired sera from a random sample of 8000 women with two pregnancies/sera within 5 years, taken from the serum bank of the Finnish Maternity Cohort (1983-98), were analysed for HPV-6, -11 and -16 antibodies. For 23-31-year-old women, HPV-16 incidence increased over the period 1983-97. HPV-16 seroprevalence increased from 17% in 1983-85 to 24% in 1995-97, but HPV-6 and HPV-11 prevalence was stable at 9-12% throughout the study period. Epidemic spread of the oncogenic HPV-16, but not the non-oncogenic HPV-types, throughout the 1980s and 1990s preceded an increase in the incidence of cervical carcinoma in fertile-aged Finnish women.