2023. Investigation The Effect of Pfizer , AstraZeneca , and Sinopharm Vaccines Against SARS-CoV-2 in Iraq Using Cluster of Differentiation 4 (CD4 ) and Vitamin D3. Iraqi Journal of Science. 64, 10 (Oct. 2023), 5011–5020. DOI:https://doi.org/10.24996/ijs.2023.64.10.10.