FEATURES OF THE COURSE OF COVID-19 IN CHILDREN DEPENDING ON HUMORAL IMMUNITY AGAINST TETANUS

Abstract

SUMMARY. The aim of the study was to find out the peculiarities of the course of COVID-19 in children depending on the state of post-vaccination immunity against tetanus toxin, assessing their level of humoral immunity against tetanus.

Materials and methods. 73 children aged 6 to 18 were examined, among them 45 had clinical manifestations of laboratory-confirmed SARS-CoV-2 infection and 28 children had no signs of COVID-19. The clinical course of the disease and laboratory indicators (C-reactive protein, ESR, D-dimer, hemoglobin level, the count of WBC and platelets) were evaluated. According to the severity of the course of the disease, 2 groups were formed: 17 children with a mild course of COVID-19 made up the first group, 28 patients with a medium-severe and severe course of the disease – the second group. Children without any manifestations of infectious diseases (28 people) made up the control group. The presence of specific immunoglobulins G against tetanus was determined in all children by immunoenzymatic method (Тetanus Elisa IgG, Vircell). This technique is based on the determination of the index of class G antibodies to tetanus toxin by the ratio of the optical density of a certain serum sample to the cut-off average value of the optical density. If the antibody index is less than 9, the result is considered negative (immunoglobulin G to tetanus toxin is absent), 9 to 11 is doubtful, more than 11 is a positive result (class G antibodies to labor toxin are present). The result was estimated as negative (the specific antibodies were absent) and as positive (the specific antibodies were present). Statistical analysis was carried out with the help of the program “Stat Plus” (Shapiro-Wilk tests, meanSD in the case of correct distribution of the trait, median, upper and lower quartiles in case of incorrect distribution, χ² test, Kruskal-Wallis test).

Results and discussion. The level of humoral immunity against tetanus toxin was significantly different in the comparison groups. In the control group (children without signs of the Coronavirus disease), 96.4 % of cases had a positive result for the presence of specific immunoglobulins G to tetanus toxin, while 37.8 % of children with symptoms of COVID-19 had the positive result. When comparing two groups of patients with COVID-19, in the first group (children with a mild course of infection), the positive result for the presence of specific immunoglobulins G to tetanus toxin was 76.5 %, in the second group (children with a moderate and severe course of the disease) – in 14.3 % of the patients.

Clinical and laboratory features of mild course of COVID-19 in children (observation group I) are significantly shorter duration of hyperthermic syndrome, significantly lower levels of pro-inflammatory markers (ESR, CRP, leukocyte count), D-dimer and duration of treatment, in observation group II (children with moderate and severe course of COVID-19) are significantly higher than the above indicators..

Conclusions. In the group of children with manifestations of COVID-19, a significantly higher percentage of negative results of the test for the presence of IgG against tetanus toxin was observed compared to the control group, indicating a lower level of humoral immunity against tetanus in this group of patients. In children with a mild course of the disease, a significantly higher percentage of positive results of the test for the presence of IgG against tetanus toxin (which indicates a higher level of humoral immunity against this pathogen) was noted compared to the group of children with a moderate and severe course of the disease. Against the background of the absence of specific immunoglobulins G to tetanus toxin, there is an increase in the level of pro-inflammatory markers (number of leukocytes, ESR, CRP) and D-dimer, duration of hyperthermic syndrome and duration of treatment, which also indicates a more severe course of the disease caused by COVID-19, that is, on the background of a lower level of humoral immunity against tetanus, there is an increase in the severity of the disease caused by COVID-19.