Age and geographic variability of human papillomavirus high-risk genotype distribution in a large unvaccinated population and of vaccination impact on HPV prevalence

Background: The prevalence of infections with human papillomavirus (HPV) specific genotypes differs by age and areas. Knowledge of these differences will help predicting how prophylactic HPV vaccination and screening program could best be integrated. Objectives: To investigate variations in the HPV distribution between areas and ages in Italy and the impact of vaccination on HPV prevalence. Study design: 37,367 women aged 25-60 years who attended cervical screening in eight different areas in Northern and Central Italy were tested for HPV infection with the high-risk hybrid capture (hr-HC2) assay. hr-HC2 positive samples were genotyped by an intensive integrated strategy. Results: hr-HPV types were detected in 79.1% of HC2 positive women. HPV16 was the most frequent type, followed by HPV31, HPV18 and HPV56. A statistically significant variability in HPV type distribution between centres (overall Y,,284df 195.86 p< 0.001) was observed. No significant overall difference in the HPV type distribution was observed in the age groups 25-34, 35-44 and 45-60 years. Considering cross-protection, overall 57.6% (95%CI 56.0-59.3) of all infections by hr-HPV types was preventable by vaccination with the bivalent vaccine and 49% (95%CI 46.9-51.1) with the quadrivalent vaccine. The variability between centres was statistically significant with both bivalent (z27df = 43.8, p <0.0001) and quadrivalent vaccine (Z27df = 32.9, p <0.0001). Conclusions: We observed differences in HPV genotype distribution according to centres but not to age. Results suggest that the higher proportion of HPV16/18 related high grade CIN in younger women could be the result of faster progression and not of earlier infection by these types. (C) 2014 Published by Elsevie