THE STAND OF COLLECTIVE IMMUNITY AGAINST MEASLES IN THE POPULATION OF THE KHARKIV REGION DURING THE EPIDEMIC AND INTER-EPIDEMIC PERIOD

Abstract

SUMMARY. From 2017 to 2023, the levels of anti-measles IgG in the blood serum of 16,833 healthy residents of the Kharkiv region between the ages of 9 months and 83 years were investigated using the ELISA method. The average concentration of IgG before the outbreak of measles was 911 mIU/ml, during the rise in the incidence in 2019, it increased to 1 167 mIU/ml due to natural booster immunization at the source of infection, and during the next 3.5 years, it gradually fell to 889 mIU/ml. For children aged 0–8 years in 2019, this indicator significantly increased compared to 2017–2018 (from 1 173 to 1 678 mIU/ml), which is associated with the increase in vaccination coverage in this period. It was found that the largest number of people susceptible to measles is in the age group from 18 to 47 years old (4.3–6.5 % of negative results (lack of protective concentration of anti-measles IgG) and 7.5–10.8 % – doubtful); the minimum number of unprotected persons was determined in the age group from 48 to 57 years (0.9 % negative and 2.1 % doubtful results), and no negative results were found in people over 57 years old (probably because most of them fell ill with measles and has strong long-term protection). After the outbreak of measles in the Kharkiv region in 2022–2023, the total share of people with protective IgG levels gradually decreased to 88.3 %, so an increase in the incidence of measles in the region may occur in the near future. Taking into account that the smallest proportion of people with a protective concentration of antibodies belong to the age groups 9–17, 18–27, 28–37, 38–47 years old, it is desirable to determine the amount of anti-measles IgG in representatives of these groups, followed by additional vaccination in case of a shortage level of antibodies.