Level of Immunological Protection against Diphtheria in the Population of Dnipropetrovsk Region

Background. Diphtheria — an infectious disease, the spread of which is limited by population post-vaccination immunity. In the system of epidemiological surveillance of diphtheria, for objective assessment and prediction of epidemic situation in low intensity of epidemic process of this infection, the serological control of immunity is crucial. The objective: prognosis of epidemic situation in terms of the risk of diphtheria outbreaks in Ukraine by the detection of population post-vaccination immunity against diphtheria in Dnipropetrovsk region and evaluation of the effectiveness of widespread vaccination. Materials and methods. 483 people aged 0 to 78 years were examined in total in 2015 (children — 234, adults — 249 persons). Evaluation of specific immunity against diphtheria was carried on with the following criteria: those with levels of antibodies 0.015–0.06 IU/mL should be considered as relatively protected; 0.1–0.5 IU/ml — with average level of protection; > 1.0 IU/ml — with high level of protection. Protective antibody titer should be considered the concentration of not less than 0.1 IU/ml. Results. It was established that the level of protective immunity against diphtheria was 69.5 %. Reliable level of immunological protection of children was 70.9 %, among adults — 68.3 %. None age group had sufficient threshold level of antitoxic immunity required to stop the transmission of diphtheria pathogen. Percentage of protected persons decreased with increasing age of people (both in children and adults). This situation may create conditions for outbreaks of diphtheria in Dnipropetrovsk region. Conclusions. The presented results indicate the importance of maintaining protective antibody levels through widespread immunization of children, as well as booster vaccination among adolescents and adults that will exclude the category of susceptible layer of the population.