Abstract
Genital warts (GWs) are common, with about 5% to 10% of people having at least one episode in their lifetime. They develop about 2–3 months after infection with human papillomavirus (HPV) genotypes 6 and 11. The prophylactic quadrivalent HPV vaccine (qHPV), protects against HPV6/11 infections and diseases. In Belgium, HPV vaccines started to be reimbursed in 2007 and have been fully reimbursed since December 2008 for women 12 to 18 years old. This study aimed at evaluating the real-life benefit of qHPV vaccine introduction in Belgium on GWs by measuring both vaccine impact (VI) at a population level and the direct effect of the qHPV vaccine at an individual level (vaccine effectiveness (VE)), using data from a large sick-fund (MLOZ) reimbursement database. A first reimbursement for imiquimod (most common first-line GWs treatment in Belgium) was used as a surrogate for a first GWs episode; reimbursement of qHPV vaccine was used as surrogate for vaccination. VI was estimated by comparing the incidence of GWs before and after qHPV vaccine introduction in Belgium (ecologic evaluation). VE was assessed by comparing GWs incidences in vaccinated vs. unvaccinated women, among women eligible for HPV vaccination. VI was evaluated in 9,223,384 person-years. Overall, GWs incidence rates decreased significantly between the pre- and post-vaccination periods (-8.1% (95% CI: -15.3; -0.3) for men and women aged 18–59 years. This decrease was highest in women targeted by the HPV vaccination programme (-72.1% (95% CI: -77.9; -64.7) in women aged 16–22 years, with a 43% vaccine uptake in 2013). A significant decrease was also observed in men aged 16-22 years (-51.1%, 95%CI: -67.6; -26.2), suggesting herd-protection. VE was evaluated in 369,881 person-years. Age-adjusted VE for fully vaccinated women was 88.0% (95% CI: 79.4; 93.0). VE was higher when the first dose was given younger and remained high for over 4 years post-vaccination in all ages. High VI and VE of the qHPV vaccine were observed in a real-life setting in Belgium.
Highlights
Human papillomaviruses (HPV) are DNA viruses that can be sexually transmitted and cause infection in basal epithelial cells such as mucosal or skin membranes [1]
The largest reduction was observed in women aged 16 to 22 years, the population targeted by the qHPV vaccination programme; -72.1% (Table 1)
We observed an important qHPV VI in the population targeted by the vaccination programme with an observed decrease in genital warts (GWs) incidence rate (IR) of 72.1% between pre and post-vaccination periods; GWs IR decreased from 257.3 per 100 000 to 71.5 per 100 000 for these women
Summary
Human papillomaviruses (HPV) are DNA viruses that can be sexually transmitted and cause infection in basal epithelial cells such as mucosal or skin membranes [1]. Infection with low-risk HPV can lead to the development of genital warts (GWs); HPV types 6 and 11 are responsible for about 90% of them [4,5,6]. Between 5% and 10% of people have at least one episode of GWs in their lifetime [7,8,9] They tend to appear shortly after first sexual activity, their incidence being highest in those aged 20 and 24 years old [10,11,12,13]. They are considered as benign but unsightly, and their treatment can be long. GWs are known to cause psychological distress and to have a detrimental impact on quality of life [14, 15]
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