evidence: As reported globally and domestically, COVID-19 vaccines can produce serious side effects related to blood clots in the body which urges the temporary discontinuation of certain vaccines in some countries. Up to the present, blood clots in the veins associated with vaccines have been reported in different parts of the body, such as the brain, thigh and lower leg. In rare cases, blood clots can systemically travel to the vessel in the lung, causing blood clots in the lung (pulmonary embolism.) The cause of unusual blood clots or thrombosis chiefly involves the activation of immune system that acts against the platelets, resulting in low levels of platelets in the blood and leading to undesired blood clot formation in the body. This is, as already published on The New England Journal of Medicine, not a new adverse reaction caused by COVID-19 vaccines. (https://www.nejm.org/doi/full/10.1056/NEJMe2106315?query=TOC) In fact, it is also a possible complication during the treatment of cardiovascular diseases. Nevertheless, blood clots associated with COVDI-19 vaccines rarely happen, only 50-60 cases reported among 50-60 million administered doses.