Abstract
Background and Objectives. The severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) reached over 1.5 million cases in Kazakhstan. Antibody titers of Immunoglobulin G (IgG), and Immunoglobulin M (IgG) are the two classes of antibodies that provide information about the immune response against SARS-COV-2. This study aimed to understand the dynamics of SARS-CoV-2 immunity and identify factors affecting the changes in IgG antibody levels over time. Materials and Methods. The prospective cohort study was conducted between November 2022 and September 2023. Healthcare workers from the University Medical Center (UMC) who have had COVID-19 infection were recruited. IgG antibodies were measured in 2 moments of time. Two-way repeated measures ANOVA was used to compare the effect of independent variable between baseline and follow up measurements and time with their interaction effect on changes in IgG levels. Results. Data was available from 81 participants. All participants were seropositive for IgG both at baseline and follow up. 4% of cases were positive for IgM, without showing symptoms of disease. There was a significant decrease in IgG between baseline and follow up (12.95±3.304; 10.49±3.044; p < 0.0001). Two-way repeated measures ANOVA showed significant interaction between allergy with time and COVID-19 hospitalization (in the multi-variable model) on the changes in IgG levels between baseline and follow up measurements. Conclusions. Although antibody responses to SARS-CoV-2 exhibit a noteworthy decline in IgG they retain noticeable positivity for anti-SARS-CoV-2 (S) antibodies, reflecting a sustained anti-body-mediated humoral immune response for more than 12 months, and that these antibodies could potentially contribute to milder reinfections.