The Covid-19 pandemic has heavily impacted global health and economy and vaccination remains the primary way of controlling the infection. During the ongoing vaccination campaign some unexpected thrombotic events have emerged in subjects who recently received the AstraZeneca Vaxzevria vaccine or the Johnson and Johnson (Janssen) vaccine, two adenovirus vector-based vaccines. Epidemiological studies confirm that the observed/expected rate of these unusual thromboses is abnormally increased, especially in women in the fertile age. The characteristics of this complication, with venous thromboses at unusual sites, most frequently cerebral vein sinus but also splanchnic, often multiple associated thromboses, thrombocytopenia, and sometimes disseminated intravascular coagulation, are unique and the time course and tumultuous evolution are suggestive of an acute immunological reaction, and indeed platelet-activating anti-PF4 antibodies have been detected in a large fraction of the affected patients. Several data suggest that adenoviruses may interact with platelets, the endothelium and the blood coagulation system. Here we review the interactions between adenoviral vectors and the haemostatic system of possible relevance for the vaccine associated thrombotic thrombocytopenia syndrome, we analyse systematically the clinical data on the reported thrombotic complications of adenovirus-based therapeutics and discuss all the current hypotheses on the mechanisms triggering this novel syndrome. Although considering current evidence the benefit of vaccination clearly outweighs the potential risks, it is of paramount importance to fully unravel the mechanisms leading to the vaccine associated thrombotic thrombocytopenia syndrome and to identify prognostic factors through further research.

中文翻译：

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腺病毒与血小板和凝血的相互作用以及疫苗相关的自身免疫性血小板减少症血栓形成综合征。

Covid-19 大流行严重影响了全球健康和经济，疫苗接种仍然是控制感染的主要方法。在正在进行的疫苗接种活动期间，最近接受阿斯利康 Vaxzevria 疫苗或强生 (Janssen) 疫苗（两种基于腺病毒载体的疫苗）的受试者出现了一些意外的血栓事件。流行病学研究证实，这些不寻常血栓的观察/预期发生率异常增加，尤其是在育龄妇女中。这种并发症的特点是，在不寻常部位出现静脉血栓，最常见的是脑静脉窦，但也有内脏血栓，通常是多发性相关血栓、血小板减少症，有时还有弥散性血管内凝血，这些特点是独特的，其时间进程和混乱的演变提示着急性免疫学疾病。事实上，在大部分受影响的患者中都检测到了血小板活化抗 PF4 抗体。一些数据表明，腺病毒可能与血小板、内皮和凝血系统相互作用。在这里，我们回顾了腺病毒载体和可能与疫苗相关的血栓性血小板减少综合征相关的止血系统之间的相互作用，我们系统地分析了已报道的基于腺病毒的治疗的血栓性并发症的临床数据，并讨论了目前关于触发这一机制的所有假设新综合症。尽管考虑到目前的证据，疫苗接种的益处明显超过潜在风险，但最重要的是充分阐明导致疫苗相关血栓性血小板减少综合征的机制并通过进一步研究确定预后因素。