Kolaib TM, Sabry RM. Heterologous COVID-19 vaccinations of Covishield/Astrazenica and Pfizer/Biontech: a case report. Int J Res Med Sci [Internet]. 2021 Oct. 28 [cited 2025 Sep. 19];9(11):3454-6. Available from: https://www.msjonline.org/index.php/ijrms/article/view/10207