Incidence, prevalence, and clearance of type-specific human papillomavirus infections: The Young Women's Health Study.

The natural history of type-specific human papillomavirus (HPV) infections was examined in a cohort of 331 women aged 18-35 years who self-referred for routine gynecological care. Participants underwent a gynecological examination at baseline and at approximately 4 and approximately 10 months after baseline. Cervical samples were collected for HPV testing and genotyping at each visit, as was information on reproductive, sexual, and medical histories. The rate of new HPV infections was 2.9% per month; the highest rates were observed for HPV types 16, 39, 84, and 51. Among women who tested negative for HPV at baseline, the cumulative probability of acquiring an oncogenic HPV strain during a 12-month follow-up period was 0.32, compared with 0.18 for nononcogenic strains. Women who had had >/=1 new male sex partner in the recent past were significantly more likely to acquire a new HPV infection (relative hazard, 2.39; 95% confidence interval, 1.20-4.76). The median time to clearance of infection was significantly longer for oncogenic strains (9.8 months) than for nononcogenic strains (4.3 months).