Abstract
A fully government-funded human papillomavirus (HPV) vaccination program started in 2007 in Spain (only 11–14-year-old girls). The first of those vaccinated cohorts, with the quadrivalent vaccine (Gardasil), turned 25 years old in 2018, the age at which cervical cancer screening begins in Spain. The current study could provide the first evidence about the effectiveness of the quadrivalent vaccine against HPV in Spain and the influence of age of vaccination. The present ambispective cohort study, which was conducted on 790 women aged 25 and 26 years old, compares the rate of HPV prevalence and cytologic anomaly according to the vaccination status. The overall infection rate was 40.09% (vaccinated group) vs. 40.6% (non-vaccinated group). There was a significant reduction in the prevalence of HPV 6 (0% vs. 1.3%) and 16 (2.4% vs. 6.1%), and in the prevalence of cytological abnormalities linked to HPV16: Atypical Squamous Cells of Undetermined Significance (ASCUS) (2.04% vs. 14%), Low-grade Squamous Intraepithelial Lesions (LSIL) (2.94% vs. 18.7%) and High-grade Squamous Intraepithelial Lesion (HSIL) (0% vs. 40%), in the vaccinated group vs. the non-vaccinated group. Only one case of HPV11 and two cases of HPV18 were detected. The vaccine effectively reduces the prevalence of vaccine genotypes and cytological anomalies linked to these genotypes.
Highlights
The expected benefits of vaccination against human papillomavirus (HPV) infection are a reduction in the prevalence of infection, cytological abnormalities in the cervix and genital warts
There were no statistically significant differences when comparing the rates of Atypical Squamous Cells of Undetermined Significance (ASCUS), Low-grade Squamous Intraepithelial Lesions (LSIL) and High-grade Squamous Intraepithelial Lesion (HSIL) between the vaccinated and the non-vaccinated group (Table 5)
When we repeated the sub-analysis on vaccination age and rate of ASCUS and LSIL, we did not find significant differences for ASCUS, showing an OR 0.7 (95%CI: 0.30–1.62), but for LSIL, the prevalence is the highest in the group vaccinated late (16.8% vs. 6.4%) with an OR 2.96 (95%CI: 1.41–6.23; p = 0.01), making it three times more likely to present an LSIL cytology if vaccination is performed after 15 years old
Summary
The expected benefits of vaccination against human papillomavirus (HPV) infection are a reduction in the prevalence of infection, cytological abnormalities in the cervix and genital warts. In Spain, a government-funded program with the quadrivalent vaccine (Gardasil®, covering HPV types 6-11-16-18) was established in 2007 for 11–14-year-old girls. In 2018, the first cohort of vaccinated women was screened at the age of 25 years old, the age when the national screening program against cervical cancer begins in Spain [7]. One study published in 2017 reported an effectiveness of 77% after three doses of the vaccine against genital warts [8]. Another study published in 2020 suggests that a high vaccine uptake with quadrivalent vaccine provides direct benefits against genital warts in the vaccinated cohorts, and extends protection through a herd effect to unvaccinated men [9]. In Spain, no data is available regarding the effectiveness after a 12-year follow-up on cytological abnormalities
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