Contribution of Vaccination to the Reduction of Infectious Mortality in Ukraine in the Second Half of the 20th and Early 21st Century: A Comparative Population Based Study of the Dynamics and Structure of Infectious Mortality and Incidence.

Our work presents an epidemiological analysis of the dynamics and structure of the annual indicators such as Cumulative Incidence, Mortality Rate (MR), and Case Fatality Rate for infections preventable by vaccines (vaccine-preventable infections-VPIs) in Ukraine between 1944 and 2015 compared to the same indicators for infections not preventable by vaccines (nonvaccine-preventable infections-non-VPIs). In 1965, the proportion of all infectious diseases in the context of mortality (7.47%), and especially of VPI (3.77%), including those registered among children aged 0-14 years (2.12%), testifies to the low profile of infectious diseases by the time of routine vaccination introduction. The analyses of these particular data are important with respect to the role of vaccination programs in reducing not only the total infectious mortality but also mortality related to VPIs in the twentieth century. Interestingly, in Ukraine between 1965 and 2015, similar rates of mortality reduction were observed in both the total population (1.6-2.6 times) and in children under 14 (15.2-20.4 times) for both VPIs and non-VPIs. During the 1944-2015 period in Ukraine, the reduction of MR of VPI (tuberculosis, diphtheria, tetanus, pertussis, poliomyelitis, measles, and hepatitis B) varied greatly, ranging from 40.5 times (tetanus) to 1,061.1 times (measles), but in general, the reduction incidence rate of VPI was significantly lower ranging from 42.4 times (measles) to 471.1 times (diphtheria). The ratio of incidence and mortality reduction in percent shows the contribution of vaccination to the mortality reduction for various infections during 1944-2015. This ratio ranged from 0% (tuberculosis) to 84.9% (tetanus), provided that the reduction of the VPI incidence 100% depends on vaccine effects. Thus, we can assume that the observed reduction in mortality for some VPIs was, in part, caused by factors not associated with vaccines.