Impact of previous infection and body mass index on interferon-gamma and immunoglobulin G level generated against three types of vaccines available in Iraq

Background: Due to increased vaccination rates and the continued spread of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus, many people are developing "hybrid immunity " to the virus. On the other hand, a high body mass index (BMI) has been associated with a reduced immune response to vaccination. the aims of this study was to measuring the level of immunoglobulin G (IgG) and interferon-gamma (IFN-gamma) generated against different types of vaccines in vaccinated individuals with and without previous infection and with BMI. a cross-sectional study was conducted between November 2021 and April 2022. Methods: A blood sample was obtained from 174 vaccinated persons. SARS-CoV-2 IgG levels and IFN-gamma were detected using SARS-CoV-2 IgG II quant and ELISAtechniques, respectively. statistical Analysis Used IBM SPSS version 24 software was used. Quantitative results are indicated as mean +/- standard deviation. The statistical significance level was set at P < 0.05. Results: There was no statistically significant difference in IgG and IFN-gamma mean levels between the vaccinated individual with and without confirmed previous infection. However, there was a significant difference in the case of the AstraZeneca vaccine regarding IgG levels only. The mean antibody concentration of patients with normal weight who received the Pfizer vaccine showed a slightly significant difference. Regarding the IFN-gamma level, there was a significant difference among the three types of vaccines in obese individuals. Conclusion: Previous infection with coronavirus disease-2019 seems to have no effect on IgG and IFN-gamma levels after vaccination. In addition, normal-weight individuals might possibly respond better to the vaccine and produce more antibody levels.