[Epidemiological assessment of an effectiveness of vaccinations]

The study deals with the notion of the effectiveness of vaccination in relation to vaccine efficacy and the performance of the vaccination programs. The types of epidemiological studies used in assessment of vaccine effectiveness are presented and listed are the most common sources of bias in those studies. Basic formulas for calculation of vaccine efficiency coefficient are given as applied for cohort and case-control studies. Ways of estimation of vaccine effectiveness in outbreaks of epidemics are presented in relation to the degree of vaccine coverage and herd immunity effect. Effectiveness is analyzed as one of the many aspects in evaluation of the epidemiological impact of vaccinations.