You should not get the covishield vaccine if 1. You experienced a severe allergic reaction after a previous dose of this vaccine. 2. People with hypersensitivity to the active substance or any of the ingredients of this vaccine. People who experienced severe allergic reaction to any ingredients of this vaccine. 3. Patients who have a history of major blood clotting ( venous and/or arterial thrombosis) in combination with a low count of platelets ( that is thrombocytopenia) after the shot of any covid 19 vaccine. Here it is important to mention that acutely unwell and hospitalized (with or without intensive care) patients due to any illness temporarily should not take a covid 19 vaccine.