Abstract Background: According to the WHO dash board 2021, it has been estimated that more than 234 million who confirmed COVID-19 cases, have been reported, and more than 6 billion vaccine doses have been administered worldwide, where thyroid dysfunction appeared to be a growing event, which might be associated with SARS-CoV-2 infection; raising the issue for proper evaluation and highlights a path for a new challenge, and novel research field. Patients and Methods: A young teenager male with no history of any previous medical condition or any special habit of medical importance, developed thyroid dysfunction post COVID-19 vaccination with viral vector vaccine diagnosed by multidisciplinary approach and evaluated by clinical examination, laboratory investigations and thyroid imaging, in Egypt. For 1-2 days post vaccination, he developed the normal expected side effects of the vaccine, in the form of low-grade fever reaching up to 38ºC, mild myalgia, infrequent headache. So, antipyretic was given in the form of paracetamol. 7-10 days following COVID-19 viral Vector vaccine, he started to develop palpitation, progressed through a whole one and half month post vaccination to appear on moderate exertion, then on very mild exertion, progressed to occur at rest, accompanied by an increase sensation to hot weather. On examination: Regular pulse but at rate of 120/min at rest, temperature 37ºC, no lymphadenopathy, normal thyroid without any swellings on palpation, tachycardia, while other systems were normal. There was mild to moderate cervical pain, and anterior neck pain region. Results: Laboratory investigations revealed elevated liver enzymes 2-3 folds, TSH=0.002Uiu, T3=15.95pg/ml, T4= 2.7ng/dl, with other labs within normal values. Cardiography showed hyperdynamic circulation, thyroid ultrasonography detected a picture suggestive of Graves' disease, while Tcm thyroid scan confirmed the diagnoses. The teenager male was confirmed to have Graves' disease/thyroid dysfunction and elevated liver enzymes as well, under follow-up. Conclusions: It seems that the viral vector vaccine for COVID-19 may be a possible initiator and/or triggering factor for susceptible subjects with either a family history or not. It could be also, causing flaring up a hidden inactive disease with rapid activation to these susceptible subjects.