Abstract
The impact of past COVID-19 infection on the immune system remains unidentified. So far, several papers have revealed the dependence between the count of lymphocytes and their subsets and the outcome of an acute disease. However, still there is little information about long-term consequences, particularly in the pediatric population. We attempted to verify whether a dysregulation of the immune system may be the reason for observed complications after past COVID-19 infection. Hence, we tried to prove that abnormalities in lymphocyte subpopulations are found in patients a certain time after the COVID-19 infection. In our paper, we enrolled 466 patients after SARS-CoV-2 infection, and evaluated their subsets of lymphocytes within 2-12 months after infection and compared them to the control group assessed several years before the pandemic. It occurred that main differences are observed in CD19(+) lymphocytes and the index CD4(+)/CD8(+) lymphocytes. We believe that this is only the introduction to further investigation of the immune system of pediatric patients post-COVID-19 infection.