在多项研究中,Moderna 或 Pfizer-BioNTech mRNA 疫苗并未显示会增加血栓风险。然而,两种 COVID-19 疫苗与一种极为罕见的综合征有关,这种综合征被称为疫苗诱发的血栓性血小板减少症(VITT)。它于 2021 年 3 月被发现与阿斯利康 COVID-19 疫苗有关,后来又与强生 COVID-19 疫苗有关。在极少数情况下(百万分之 2 到 20)身体产生的抗体作为疫苗的副作用会导致血小板不受控制地激活。这会导致血小板计数低和血块形成。
这种罕见抗体的出现是一个随机事件,与一个人的病史或任何特定条件没有已知关联。“无法预测谁可能会产生触发 VITT 的罕见抗体,”Abou-Ismail 说。“虽然与其他人群相比,它在年轻女性中更为常见,但即使在该群体中也极为罕见。”
The Moderna or Pfizer-BioNTech mRNA vaccines have not been shown to increase the risk of blood clots in multiple studies. However, two COVID-19 vaccines are associated with an extremely rare syndrome known as vaccine-induced thrombotic thrombocytopenia (VITT). It was discovered in March 2021 in connection to the AstraZeneca COVID-19 vaccine and then later with the Johnson & Johnson COVID-19 vaccine. In rare cases—2 to 20 per million—antibodies that the body produces as a side effect of the vaccine lead to uncontrolled activation of platelets. This causes both low platelet counts and blood clots to form.
The occurrence of this rare antibody is a random event without a known association with a person’s medical history or any particular conditions. “There’s no way to predict who’s likely to develop the rare antibody that triggers VITT,” Abou-Ismail says. “While it is a little more common in younger women compared to other populations, it remains exceedingly rare even in that group.”