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

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.