Department of Haematology, Mid & South Essex University Hospital NHS Foundation Trust, Prittlewell Chase, Westcliff-on-Sea SS0 0RY, UK.
Department of Haematology, Queen Mary University of London, Mile End Road, London E1 3NS, UK.
Molecules. 2021 Aug 18;26(16):5004. doi: 10.3390/molecules26165004.
The thrombotic thrombocytopenia syndrome (TTS), a complication of COVID-19 vaccines, involves thrombosis (often cerebral venous sinus thrombosis) and thrombocytopenia with occasional pulmonary embolism and arterial ischemia. TTS appears to mostly affect females aged between 20 and 50 years old, with no predisposing risk factors conclusively identified so far. Cases are characterized by thrombocytopenia, higher levels of D-dimers than commonly observed in venous thromboembolic events, inexplicably low fibrinogen levels and worsening thrombosis. Hyper fibrinolysis associated with bleeding can also occur. Antibodies that bind platelet factor 4, similar to those associated with heparin-induced thrombocytopenia, have also been identified but in the absence of patient exposure to heparin treatment. A number of countries have now suspended the use of adenovirus-vectored vaccines for younger individuals. The prevailing opinion of most experts is that the risk of developing COVID-19 disease, including thrombosis, far exceeds the extremely low risk of TTS associated with highly efficacious vaccines. Mass vaccination should continue but with caution. Vaccines that are more likely to cause TTS (e.g., Vaxzevria manufactured by AstraZeneca) should be avoided in younger patients for whom an alternative vaccine is available.
血栓性血小板减少性紫癜综合征（TTS）是 COVID-19 疫苗的一种并发症，涉及血栓形成（常为脑静脉窦血栓形成）和血小板减少症，偶尔还伴有肺栓塞和动脉缺血。TTS 似乎主要影响 20 至 50 岁之间的女性，目前尚未明确确定任何易患风险因素。该病症的特征是血小板减少症、D-二聚体水平高于通常观察到的静脉血栓栓塞事件、无法解释的低纤维蛋白原水平和血栓恶化。也可能发生与出血相关的纤维蛋白溶解亢进。已发现与肝素诱导的血小板减少症相关的类似结合血小板因子 4 的抗体，但患者没有肝素治疗的暴露史。目前，许多国家已经暂停为年轻人使用腺病毒载体疫苗。大多数专家的主流意见是，感染 COVID-19 疾病（包括血栓形成）的风险远远超过与高效疫苗相关的 TTS 的极低风险。应继续大规模接种疫苗，但需谨慎。对于有替代疫苗的年轻患者，应避免使用更可能引起 TTS 的疫苗（例如阿斯利康生产的 Vaxzevria）。
