Declines in Human Papillomavirus (HPV)-Associated High-Grade Cervical Lesions After Introduction of HPV Vaccines in Connecticut, United States, 2008-2015.

Background: Trends in human papillomavirus (HPV)-associated cervical lesions can provide an indication of vaccine impact. Our purpose was to measure trends in cervical lesions during 2008-2015 and to consider possible explanations including vaccination coverage, changes in screening for cervical cancer, and risk behaviors for acquiring HPV.

Methods: Connecticut (CT) implemented mandatory reporting of cervical intraepithelial neoplasia grades 2/3 and adenocarcinoma in situ (cervical intraepithelial neoplasia grade 2 or higher [CIN2+]) in 2008. Trends by age and birth cohort were modeled using negative binomial regression and change-point methods. To evaluate possible explanations for changes, these trends were compared to changes in HPV vaccination coverage, cervical cancer screening, an antecedent event to detection of a high-grade lesion, and changes in sexual behaviors and Chlamydia trachomatis, an infection with similar epidemiology to and shared risk factors for HPV.

Results: A significant decline in CIN2+ was first evident among women aged 21 years in 2010, followed by successive declines in women aged 22-26 years during 2011-2012. During 2008-2015, the rates of CIN2+ declined by 30%-74% among women aged 21-26 years, with greater declines observed in the younger women. Birth cohorts between 1985 and 1994 all experienced significant declines during the surveillance period, ranging from 25% to 82%. Ecological comparisons revealed substantial increases in HPV vaccination during this time period, and more modest reductions in cervical cancer screening and sexual risk behaviors.

Conclusions: The age and cohort patterns in our data suggest that declines in CIN2+ during 2008-2015 are more likely driven by HPV vaccination, introduced in 2006, than by changes in screening or risk behavior.