Introduction: COVID-19 vaccine have been indicated to successfully decrease the hazard for symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection furthermore associated hospitalisations. Objective: To study the immune response among different types of SARS-CoV-2 vaccines. Methods: This study includes 100 vaccinated individuals (43 Sinopharm, 30 AstraZeneca and 27 Pfizer) with one or two doses from different health centres in Baghdad. During the period from April 2021 to the end of May 2021, SARS-CoV-2 IgG and SARS-CoV-2 IgM levels were detected using AFIAS-6 device depending on FIA (Fluorescence Immunoassay) technique. Results: 93% of the cases were positive for IgG levels, and negative in 7% cases. Coronavirus IgM concentrations for all individuals were negative. The highest IgG mean level was seen in vaccinated persons with Pfizer than AstraZeneca (34.41, 26.29 respectively) and the lowest mean value was detected in Sinopharm (23.76). There was a significant elevation in IgG levels in the previously infected group in comparison with non-infected individuals. IgG levels decrease in antibody responses to SARS-CoV-2 in older individuals compared to younger participants. Also, results reported that SARS-CoV-2 IgG levels increased in males who were vaccinated with Pfizer and AstraZeneca more than females, while there is a significant decrease in IgG levels in vaccinated males with Sinopharm as compared to females. Conclusion: Different vaccines against SARS-CoV-2 produce different levels of IgG.
