Hematology Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.
Hematology Research Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia.
Int J Lab Hematol. 2022 Apr;44(2):424-429. doi: 10.1111/ijlh.13774. Epub 2021 Nov 30.
The development of anti-platelet factor 4 (PF4) antibodies is linked to a rare thrombotic complication described now as vaccine-induced immune thrombotic thrombocytopenia (VITT). This clinical syndrome with thrombosis and thrombocytopenia was reported after exposure to the Oxford-AstraZeneca COVID-19 vaccine, ChAdOx1 nCoV-19 vaccine (AZD1222), and Ad26.COV2.S vaccine (Janssen/Johnson & Johnson). In the absence of the clinical features, the incidence of positive anti-PF4 antibodies in asymptomatic individuals post-vaccination is unclear.
The aim of this study was to evaluate the development of anti-PF4 antibodies in asymptomatic individuals 14-21 days after receiving the first dose of ChAdOx1 nCoV-19 vaccine (AZD1222) and BNT162b2 vaccine. Prospectively, we collected serum from individuals before and after ChAdOx1 nCoV-19 vaccine and BNT162b2 vaccine and measured anti-PF4 antibodies using the Asserachrom HPIA IgG ELISA (Stago, Asnieres, France).
We detected positive anti-PF4 antibodies in 5 of 94 asymptomatic individuals post-vaccine with a rate of 5.3% with low titers (OD 0.3-0.7). Four of 5 individuals who tested positive after the vaccine had also positive anti-PF4 antibodies before the vaccine, which indicates that a majority of the positive results are due to preexisting anti-PF4 antibodies. We did not find a relation between the development of anti-PF4 antibodies and the immune response to the vaccine, status of prior COVID-19 infection, and baseline characteristics of participants. None of the participants developed thrombosis nor thrombocytopenia.
Our results provide new evidence to guide the diagnostic algorithm of suspected cases of VITT. In the absence of thrombosis and thrombocytopenia, there is a low utility of testing for anti-PF4 antibodies.
抗血小板因子 4（PF4）抗体的产生与一种罕见的血栓并发症有关，现在被描述为疫苗诱导的免疫性血栓性血小板减少症（VITT）。这种伴有血栓形成和血小板减少的临床综合征在接触牛津-阿斯利康 COVID-19 疫苗、ChAdOx1 nCoV-19 疫苗（AZD1222）和 Ad26.COV2.S 疫苗（Janssen/Johnson & Johnson）后被报道。在没有临床特征的情况下，接种疫苗后无症状个体中抗 PF4 抗体呈阳性的发生率尚不清楚。
本研究旨在评估接种 ChAdOx1 nCoV-19 疫苗（AZD1222）和 BNT162b2 疫苗后 14-21 天无症状个体中抗 PF4 抗体的产生情况。前瞻性地，我们收集了 ChAdOx1 nCoV-19 疫苗和 BNT162b2 疫苗接种前后个体的血清，并使用 Asserachrom HPIA IgG ELISA（Stago，Asnieres，法国）测量抗 PF4 抗体。
我们在 94 名无症状个体中有 5 名在接种疫苗后检测到抗 PF4 抗体阳性，阳性率为 5.3%，且抗体滴度较低（OD 0.3-0.7）。5 名接种疫苗后检测呈阳性的个体中，有 4 名在接种疫苗前也有抗 PF4 抗体阳性，这表明大多数阳性结果是由于预先存在的抗 PF4 抗体。我们没有发现抗 PF4 抗体的产生与疫苗的免疫反应、既往 COVID-19 感染状态和参与者的基线特征之间存在关系。
我们的结果为疑似 VITT 病例的诊断算法提供了新的证据。在没有血栓形成和血小板减少的情况下，检测抗 PF4 抗体的效用较低。
