Clinical and Epidemiological Features of Pertussis in Children at Incomplete Vaccination Coverage

Objective: to study the clinical and epidemiological features of pertussis in children at incomplete coverage of the population with routine immunization. Materials and Methods. To achieve this goal, we have evaluated the epidemiological situation of pertussis and studied the features of the clinical course of the disease in 296 children aged from 1 month to 14 years (data from the annual reports for the period of 1987–2012). Additional research methods included: complete blood count, chest X-ray examination, enzyme immunoassay, polymerase chain reaction and bacteriological method. Evaluation of immune status was based on a comprehensive study of indicators of the overall reactive potential of the body by studying the qualitative and quantitative characteristics of hemograms. Statistical analysis was performed using analysis software package Microsoft Excel 2003. Results. In the Donetsk region, as in whole in Ukraine, there was a tendency to reduce the incidence of pertussis (12.4–1.5 per 100 thousand population), with periodic ups and downs every 2–3 years. In 2011, there was another rise in the incidence of pertussis infection: incidence exceeded the previous year level by 3 times and national figure — by 1.5 times (2.9 per 100 thousand population). Increased incidence was observed in every second administrative territory; in some of them it increased by 10–18 times compared to last year. Epidemic worsening was determined on a background of incomplete coverage with routine immunization of the population due to the insufficient supply of vaccines in Donetsk region in the last 3 years — 77 % (2009), 51 % (2010) and 56 % (2011). Age groups which are most at-risk for pertussis, as before, are infants (132.1 per 100 thousand population) who were not subject to vaccination by age or have not received the full course of vaccination, as well as at-risk children aged 5–9 years (46.8 per 100 thousand population), adolescents (1.42 per 100 thousand population). Change in the epidemic situation has had an impact on the nature of the clinical course of pertussis: the number of severe forms increased — unvaccinated children accounted for 84.0 %, and symptomatic forms of the disease were registered (in the foci of infection 85–92 %). Conclusions. Stabilization of the epidemic situation with pertussis has been promoted by a number of preventive measures: a) the development of legislative documents to improve the surveillance system; b) monitoring of changes in serotypes of the pathogen; c) improvement of laboratory diagnosis of diseases by introducing modern methods of research; d) annual sufficient supply of regions with pertussis vaccines in accordance with the requests; e) timely and complete vaccination coverage according to the annual plan of immunization; f) professional training of primary health care practitioners. Prevention of involvement in the epidemic process of young children and schoolchildren is possible by maintaining stable high immunization coverage of children in decreed terms by using an effective vaccine, availability of affordable and informative methods of immunity evaluation, as well as a reliable bacteriological diagnosis of pertussis. Currently, along with increased coverage of routine vaccination, surveillance of this infection is particularly important, which enables to carry out antiepidemic measures in the form of early diagnosis of pertussis in exposed children. In modern conditions, the classic symptoms of the disease still remain in vaccinated and unvaccinated children, but there are differences in the severity of pertussis in children with poor premorbid background. Diagnosis of pertussis, especially among infants, remains a challenge for practical public health