Human papillomavirus vaccines effectiveness to prevent genital warts: A population-based study using health system integrated databases, 2009-2017.

OBJECTIVES

To assess the effectiveness of the HPV vaccines in preventing genital warts (GW) in women aged 14-23 years and to estimate the incidence of GW in the whole population aged from 14 to 65.

DESIGN

Population-based retrospective cohort study using real-world data from the Valencia health system Integrated Databases (VID).

STUDY POPULATION

All subjects aged 14-65 years residing in the Valencia Region during 2009-2017 (n = 4,492,724), including a cohort of 563,240 females aged 14-23 years followed-up for the vaccine effectiveness (VE) estimations.

MAIN OUTCOME MEASURES

Incident cases of GW defined as the first activation of GW-related codes (ICD-9-CM 078.11 or ICD-10-CM A63.0) in hospital, primary and specialized care during the study period. Adjusted VE was estimated as (1-Relative Risk (RR)) × 100 by a negative binomial Bayesian model.

RESULTS

There were 23,049 cases of GW in the overall population and 2,565 in the females' cohort 14-23 years old. The incidence rate (IR) (in 100,000 persons-year) was 69.1 (95% CI 68.21-69.99) in the population overall, being higher in men (72.73; 95% CI 71.45-74.04). The IR of GW was 104.08 (95% CI 100.79-108.94) in the cohort of young women. The RR of GW increased with age from 14 to 21 years, reaching a plateau from 21 to 23. The VE of a complete schedule was 74% (95% CrI 68-79) for quadrivalent HPV vaccine (HPV4v). No effectiveness was seen with a full vaccination course with the bivalent HPV vaccine (HPV2v) in girls up to 21 years old. GW IR tends to be higher in unvaccinated cohorts covered by HPV4v vaccine than in unvaccinated cohorts not covered by HPV4v vaccine.

CONCLUSIONS

A complete HPV4v vaccination schedule was 74% effective in reducing GW in our population. Our results also suggest an indirect protection to unvaccinated and HPV2v vaccinated girls.