text: COVID 19 vaccines and thrombosis with thrombocytopenia syndrome To combat COVID 19 scientists all over the world have expedited the process of vaccine development Although interim analyses of clinical trials have demonstrated the efficacy and safety of COVID 19 vaccines a serious but rare adverse event thrombosis with thrombocytopenia syndrome TTS has been reported following COVID 19 vaccination This review using data from both peer reviewed and non peer reviewed studies aimed to provide updated information about the critical issue of COVID 19 vaccine related TTS The exact epidemiological characteristics and possible pathogenesis of this adverse event remain unclear Most cases of TTS developed in women within 2 weeks of the first dose of vaccine on the receipt of the ChAdOx1 nCoV 19 and Ad26 COV2 S vaccines In countries with mass vaccination against COVID 19 clinicians should be aware of the relevant clinical features of this rare adverse event and perform related laboratory and imaging studies for early diagnosis Non heparin anticoagulants such as fondaparinux argatroban or a direct oral anticoagulant e g apixaban or rivaroxaban and intravenous immunoglobulins are recommended for the treatment of TTS However further studies are required to explore the underlying mechanisms of this rare clinical entity b What is the context b Thrombosis with thrombocytopenia syndrome TTS usually develops within 2 weeks of the first doses of the ChAdOx1 nCoV 19 and Ad26 COV2 S COVID 19 vaccines TTS mainly occurs in patients aged 55 years and is associated with high morbidity and mortality b What is new b TTS mimics autoimmune heparin induced thrombocytopenia and can be mediated by platelet activating antibodies against platelet factor 4 Non heparin anticoagulants such as fondaparinux argatroban or a direct oral anticoagulant e g apixaban or rivaroxaban should be considered as the treatment of choice if the platelet count is 50 10 sup 9 sup L and there is no serious bleeding Intravenous immunoglobulins and glucocorticoids may help increase the platelet count within days and reduce the risk of hemorrhagic transformation when anticoagulation is initiated b What is the impact b TTS should be a serious concern during the implementation of mass COVID 19 vaccination and patients should be educated about this complication along with its symptoms such as severe headache blurred vision seizure severe and persistent abdominal pain painful swelling of the lower leg and chest pain or dyspnea The incidence of TTS is low therefore maintenance of high vaccination coverage against COVID 19 should be continued 