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Abstract

Newswise — Background: Various studies have reported on the impact of human papillomavirus (HPV) vaccines. Here we present the largest population-based investigation of genotype-specific distributions over the decade following implementation of the 4-valent HPV vaccine (HPV6/11/16/18) in the United States.

Methods: Liquid-based cervical cytology samples from individuals aged 15-30 years undergoing cervical screening throughout New Mexico were tested by broad-spectrum HPV genotyping. Weighted relative differences in HPV type-specific prevalence (RDP) and 95% confidence intervals (95%CI) were calculated comparing individuals screened in 2007-2009 (n = 95,915) to those screened in 2013-2016 (n = 103,371). Weighted logistic regression was used to estimate relative risk of type-specific HPV infections. Tests of significance were 2-sided.

Results: Genotype-specific prevalence reduced significantly for HPV16 (RDP=-52.6%, 95%CI -56.9 to -48.3), HPV18 (RDP=-62.1%, 95%CI -68.5 to -55.8), HPV31 (RDP=-34.2%, 95%CI -42.1 to -26.3) and HPV33 (RDP=-31.8%, 95%CI -48.4 to -15.1). The RDP increased for other carcinogenic HPV types by 19.5% (95%CI +14.3 to + 24.6) when excluding HPV16/18. Large reductions in HPV6/11 RDP were observed but overall, non-carcinogenic, non-vaccine types increased. Comparing females born in 1996 to those born in 1989, risk of infection with HPV6/11/16/18 decreased by 80.0% among individuals aged 21-25 years. High-grade squamous intraepithelial lesions or worse (HSIL+) decreased by 49.4% when extending the evaluation from 2007 to 2018.

Conclusion(s): HSIL+ incidence is decreasing with large reductions in the prevalence of 4-valent HPV vaccine types and non-vaccine types HPV31 and 33, reflecting vaccine cross-protection. Increases in non-vaccine HPVs may attenuate anticipated reductions in HPV-related abnormalities including cancers however the benefits of HPV vaccination remain substantial.