Evaluation of immunoglobulin G level among subjects vaccinated with different types of COVID-19 vaccines in the karbala population, Iraq

Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines represent the only way in combating the COVID-19 pandemic. Studying the differences in immune response to different types of vaccines is considered an important tool for optimizing vaccine selection and dosage required. The aim of this study was to evaluate the immunoglobulin G (IgG) concentration following vaccination with Pfizer, AstraZeneca, and Sinopharm vaccines. A cross-sectional study was conducted between November 2021 and April 2022. Methods: A blood sample was obtained from 174 vaccinated persons, IgG levels were detected using the SARS-COV-2 IgG II Quant assay on the ARCHITECT I system. Statistical analysis used IBM SPSS VERSION 24 software. Quantitative results are indicated as mean ± standard deviation. The statistical significance level was set at P < 0.05. Results: Out of 60.3%, 33.9%, and 5.7% had received Pfizer, Sinopharm, and AstraZeneca vaccines, respectively. Ninety participants were men and 84 were women with ages ranging from 18 to 70 years. IgG concentrations were higher in participants vaccinated with Pfizer's vaccine. There were significant differences among the three types of vaccine within age groups. The mean IgG concentration was higher in male participants vaccinated with Pfizer and AstraZeneca. No significant variation was observed between the first and second doses for each type of the three vaccines. The IgG concentration for a vaccination with Pfizer varied significantly among the weeks after vaccination, the maximum concentration was seen between the 6th and 7th weeks. Conclusions: Participants vaccinated with the Pfizer vaccine produce the highest antibody concentration as compared to other vaccines, especially in male participants. Younger participants produce higher amount of antibody response.