Varicella infection in a non-universally vaccinated population: Actual epidemiology in Bulgaria (2013-2015)

J Infect Public Health. 2018 May-Jun;11(3):326-330. doi: 10.1016/j.jiph.2017.09.023. Epub 2017 Oct 7.


Background: Varicella is a common and usually mild disease but it has great importance in regard to general infectious morbidity. The current study aimed to characterize possible risk factors of varicella epidemiology in Bulgaria, a country where infection follows its natural epidemiological pattern as no mandatory or recommended vaccine is currently applied.

Methods: Administrative regions of Bulgaria were used as units of observation and a set of sociodemographic and economic determinants, as well as geographic location (south or north) were tested for associations with the mean 3-year varicella incidence rates (2013-2015).

Results: The proportion of urban population, proportion of females, number of health care units and proportion of urban population aged <10 years were the four sociodemographic variables most strongly and significantly correlated (p<0.05) with varicella frequency (Spearman's rank correlation coefficients of 0.62, 0.47, 0.43, and 0.38, respectively). After reducing the number of intercorrelated factors to a few principal components and accounting for confounders, the demographic component and geographic location remained most robustly associated with varicella incidence in Bulgaria (adjusted R2 of 0.51, p<0.001).

Conclusions: The results obtained identify important determinants in the local epidemiology of varicella and show that community characteristics should be considered, to improve our understanding of varicella distribution.

Keywords: Chickenpox; Epidemiology; Notifiable infectious diseases; Vaccine-preventable diseases; Varicella zoster virus.

MeSH terms

  • Bulgaria / epidemiology
  • Chickenpox / epidemiology*
  • Chickenpox / prevention & control
  • Chickenpox / virology
  • Child
  • Child, Preschool
  • Demography
  • Female
  • Geography
  • Herpes Zoster / epidemiology
  • Herpes Zoster / virology
  • Herpesvirus 3, Human / isolation & purification
  • Herpesvirus 3, Human / physiology
  • Humans
  • Incidence
  • Infant
  • Infant, Newborn
  • Male
  • Population Surveillance*
  • Risk Factors
  • Socioeconomic Factors
  • Vaccination / statistics & numerical data*