Epidemiological impact of the human papillomavirus vaccination program on genital warts in Portugal: A retrospective, chart review study

Abstract

Background: The quadrivalent human papillomavirus (HPV) vaccine was introduced in the Portuguese National Immunization Program in October 2008, targeting 13-year-old girls. This study aimed at evaluating the impact of HPV vaccination on the epidemiology of genital warts (GWs) in Portugal.

Methods: Observational, retrospective chart review study conducted at two free-of-charge walk-in sexually transmitted diseases (STD) clinics in Lisbon region. The medical records of all patients attending a first STD consultation at the study centers between May 2006 and December 2017 (observation period) were reviewed. The number of patients diagnosed with GWs and/or chlamydial infection at each year was documented and used to determine yearly prevalence of both conditions throughout the observation period. We broke down the observation period into pre-vaccination (May 2006 to December 2008) and vaccination (January 2009 to December 2017) periods.

Results: Most patients were male (69.5%) and aged ≥ 25 years (78.1%). The majority of male patients were men who have sex with women (62.0%). Marked decreases in the prevalence of GWs between the last year of the pre-vaccination period (2008) and the last year of the observation period (2017) were found for female patients aged ≤ 19 and 20-24 years (86.8% and 77.4%, respectively). Lower decreases were observed for male patients of the same age groups (38.5% and 19.3%, respectively). GWs prevalence increased among patients ≥ 25 years (9.7% and 14.7% among female and male patients, respectively). Overall prevalence of chlamydial infection increased by 75.9% between 2008 and 2017.

Conclusions: This study contributes to the body of evidence showing that public HPV vaccination programs are effective in reducing the prevalence of GWs among vaccine-eligible patients. HPV vaccination program may significantly reduce the burden associated with GWs in Portugal.

Keywords: Genital warts; Human papillomavirus; Sexually transmitted diseases; Vaccination.