The involvement of viruses and SARS-CoV-2 in autoimmune diseases is well known. The recent demonstration that ChAdOx1 nCoV-19 Covid-19 (AstraZeneca) vaccine (ChA) favors the production of anti-platelet factor 4 (anti-PF4) antibodies, blood clots, and thrombocytopenia raises the question of whether other anti-CoViD-19 vaccines favor the same patterns of events.

We assessed the frequency of severe adverse events (SAEs) documented in the EudraVigilance European database up to April 16, 2021 related to thrombocytopenia, bleeding, and blood clots in recipients of ChA compared to that of recipients of the BNT162b2 Covid-19 (Pfizer/BioNTech) vaccine (BNT).

ChA administration was associated with a much higher frequency of SAEs in each AE Reaction Group as compared with that elicited by BNT. When considering AEs caused by thrombocytopenia, bleeding and blood clots, we observed 33 and 151 SAEs/1 million doses in BNT and ChA recipients, respectively. When considering patients with AEs related to cerebral/splanchnic venous thrombosis, and/or thrombocytopenia, we documented 4 and 30 SAEs and 0.4 and 4.8 deaths/1 million doses for BNT and ChA recipients, respectively. The highest risk following ChA vaccination is in young people and, likely, women of reproductive age, as suggested by hypothesized scenarios.

In conclusion, the immune reaction promoted by ChA vaccine may lead to not only thrombocytopenia and cerebral/splanchnic venous thrombosis but also other thrombotic and thromboembolic SAEs. These events are not favored by BNT vaccine. Our study may help in the evaluation of the benefit/risk profile of the ChA vaccine considering the epidemic curve present in a country.

病毒和 SARS-CoV-2 与自身免疫性疾病的关系是众所周知的。最近的研究表明，ChAdOx1 nCoV-19 Covid-19（阿斯利康）疫苗（ChA）有利于产生抗血小板因子 4（抗 PF4）抗体、血栓和血小板减少症，这引发了一个问题：其他抗 CoViD-19 疫苗是否有利于产生抗血小板因子 4（抗 PF4）抗体、血栓和血小板减少症疫苗有利于相同的事件模式。

我们评估了截至 2021 年 4 月 16 日 EudraVigilance 欧洲数据库中记录的与 ChA 接受者与 BNT162b2 Covid-19 接受者（辉瑞/ BioNTech）疫苗（BNT）。

与 BNT 引起的相比，ChA 给药与每个 AE 反应组中 SAE 的发生频率要高得多。当考虑血小板减少、出血和血栓引起的 AE 时，我们在 BNT 和 ChA 接受者中分别观察到 33 例和 151 例 SAE/100 万剂。当考虑患有与脑/内脏静脉血栓形成和/或血小板减少症相关的 AE 的患者时，我们分别记录了 BNT 和 ChA 接受者每 100 万剂中 4 例和 30 例 SAE，以及 0.4 例和 4.8 例死亡。正如假设情景所示，ChA 疫苗接种后风险最高的是年轻人，也可能是育龄妇女。

总之，ChA疫苗促进的免疫反应不仅可能导致血小板减少和脑/内脏静脉血栓形成，还可能导致其他血栓和血栓栓塞性SAE。BNT 疫苗不利于这些事件。考虑到一个国家的流行曲线，我们的研究可能有助于评估 ChA 疫苗的效益/风险状况。