Prevalence, evolution, and features of infection with human papillomavirus: a 15-year longitudinal study of routine screening of a women population in the north of Spain.

Determination of the prevalence of type-specific human papillomavirus (HPV) is important for the development of new vaccines and to prevent malignancy. The objective of this study was to determine HPV infection in two areas in the north of Spain, and their evolution in the last 15 years. Between 1991 and 2007, 7,930 fresh cervical swabs were obtained from 5,554 women (37.8 +/- 11.8 years old). From them, 425 have been followed-up for an average of 3.7 +/- 2.08 years after sampling (range 2-14.6), and 71 for 7.7 +/- 2.2 years (range 5-14). Methods based on polymerase chain reaction (PCR) were carried out. Samples from 1,598 (28.8%) women were positive for HPV: 40.9% were under 25 years of age, 34.2% in the 25-35 year age group, 27.2% in the 36-45 year age group, and 19.6% older than 45 years (P < 0.001). HPV was found in 34.4% of the women with cytological alterations versus 23% of women without cervical changes (P < 0.0001). HPV-16 was present in 25.8% of the women, although the study identified 26 different HPV genotypes. After 3 years of follow-up, HPV remained or became undetectable in 87% of the cases, and in 5 years 70.3%. The prevalence of HPV is associated with younger women and women with cytological changes in the cervix. Although HPV-16 is more prevalent, HPV types not included in available vaccines were found the most commonly. The low 3-year (even 5-year) cumulative incidence rate of HPV infection suggests that cervical screening every 3 (or even 5) years is safe and effective.