EVALUATION OF THE LEVEL OF COLLECTIVE IMMUNITY IN CHILDREN LIVING IN THE CITY OF YEKATERINBURG TO VACCINE-PREVENTABLE INFECTIONS AGAINST THE BACKDROP OF THE SPREAD OF THE COVID-19 PANDEMIC
Authors:   Yekaterinburg City Clinical and Diagnostic Center, Yekaterinburg, Sverdlovsk Oblast, Russia, Olenkova O.M. , Kovtun O.P. ,   Urals State Medical University, Yekaterinburg, Sverdlovsk Oblast, Russia, Kharitonov A.N. ,   Center for Public Health and Medical Prevention, Yekaterinburg, Sverdlovsk Oblast, Russia, Beikin Ya.B. ,   Institute of Immunology and Physiology with the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Sverdlovsk Oblast, Russia, Rybinskova E.A. ,   Center for Public Health and Medical Prevention, Yekaterinburg, Sverdlovsk Oblast, Russia
Published: July 2022

The vaccination is recognized as one of the most effective and cost-effective measures to prevent the emergence and spread of infectious diseases. There is a possibility that the COVID-19 pandemic may lead to disruption of the vaccination campaign against vaccine-preventable infections and the formation of herd immunity. The aim of the study is to assess the level of collective immunity to vaccine-preventable infections in children living in the city of Yekaterinburg, Russia, against the backdrop of the COVID-19 pandemic. Research materials and methods: an observational cohort retrospective study was conducted, which included the results of a survey of 520 children aged 1 to 18 years old in 2021 for the presence of antibodies (AB) to the pathogens of measles, whooping cough, mumps, diphtheria and poliomyelitis. As a comparison the study used materials from a survey of children conducted in 2007 - 2013 for the assessment of herd immunity to vaccine-preventable infections (n=298). So the total number of children examined was 818. Results: the proportion of seronegative individuals examined for the presence of IgG to the causative agent of diphtheria among children aged 1 to 6 years old was 6.3%, 7 to 14 years old - 4.0%, 15 to 17 years old - 0.7 % (p<0.001). The proportion of children with no antibodies to the measles virus is 11.9%, 7.6%, and 12.4%, respectively, in the age groups of 1 to 6/7 to 14/15 to 17 years old (p=0.02). The proportion of seronegative to the mumps virus among children of different ages lays within 12% to 23.8%. The share of children with the absence of protective antibody titers to the whooping cough pathogen was 51.1% in children aged 15 to 17 years old, 69.5% for 7 to 14 years old, and 62.5% for 1 to 6 years old (p<0.001). With a cut-off of 10%, the proportion of children unprotected from type I poliovirus was 9.1% in the 3 to 5 years old age group and 6.8% in the 11 to 17 years old age group. The proportion of seronegative to poliovirus type III was 11.2% and 23.9%, respectively, in the younger and older groups of children. Discussion: the most favorable state of herd immunity was found in relation to diphtheria. Alertness is caused by immunity to measles and mumps. The most alarming is the state of herd immunity to whooping cough. Conclusion: for the period 2012-2021 there was an increase in the number of children with protective antibodies to the pathogens of diphtheria, measles, mumps, and whooping cough. However, with the exception of diphtheria, in all of these infectious diseases, the level of seronegative individuals exceeds the recommended thresholds. A high proportion of seronegative individuals increases the risk of the emergence and spread of infectious diseases.