Coronavirus disease 2019 (COVID-19) has caused a global pandemic in just a few months, causing millions infected. Nearly 20% of COVID-19 patients present severe coagulation abnormalities, which may occur in almost all of the severe and critical ill COVID-19 cases. Concomitant venous thromboembolism (VTE), a potential cause of unexplained deaths, has been frequently reported in COVID-19 cases, but its management is still challenging due to the complexity between antithrombotic therapy and coagulation disorders. Based on frontline practical experience and comprehensive literature review, here a panel of experts and physicians from China and Europe developed an evidence and opinion-based consensus on the prophylaxis and management of VTE associated with COVID-19. This statement aims for clinicians treating COVID-19 and provides practical recommendations in detailed situations, for example, how to choose thromboprophylactic measures for patients with diverse severity of disease and bleeding risk, or which kind of anticoagulant should be prescribed. With limited experience on COVID19-associated VTE, this expert consensus statement should be helpful for clinicians worldwide with specific suggestions. From Pulmonary Embolism and Pulmonary Vascular Diseases Group of the Chinese Thoracic Society, Pulmonary Embolism and Pulmonary Vascular Disease Working Committee of Chinese Association of Chest Physicians, National Cooperation Group on Prevention and Treatment of Pulmonary Embolism and Pulmonary Vascular Disease, National Capacity Building Program Office for Prevention and Treatment of Pulmonary Embolism and Deep Vein Thrombosis, China Grade Center, Evidence-based Medicine Center of School of Basic Medical Sciences of Lanzhou University. Chinese Academy of Medical Sciences and Peking Union Medical College (Chen Wang) and Department of Cardiovascular Surgery and Vascular Medicine of China-Japan Friendship Hospital (Peng Liu). Evidence-based Medicine Center of Lanzhou University (Yaolong Chen); China-Japan Friendship Hospital (Jun Wan, Wanmu Xie, and Zhenguo Zhai); Affiliated Hospital of Jianghan University (Chenghong Li); Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology (Xiansheng Liu); the First Affiliated Hospital of Chongqing Medical University (Hong Chen); and the First Affiliated Hospital of Dalian Medical University (Yingqun Ji). General Hospital of Northern Theater Command (Zhuang Ma); Beijing Hospital (Xiaomao Xu); Huashan Hospital Affiliated to Fudan University (Shengqing Li); the Second Hospital of Hebei Medical University (Yadong Yuan); Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology (Xiansheng Liu and Jianping Zhao); Affiliated Hospital of Jianghan University (Chenghong Li and Ziyang Zhu); the First Affiliated Hospital with Nanjing Medical University (Xuesong Chen); Renmin Hospital of Wuhan University (Ke Hu); Wuhan Asia Heart Hospital (Zhenlu Zhang), Wuhan Pulmonary Hospital (Ronghui Du); Wuhan Jinyintan Hospital (Ming Wei); the Central Hospital of Wuhan (Yi Hu); the First Affiliated Hospital of Zhengzhou University (Zhe Cheng); and China-Japan Friendship Hospital (Shuai Zhang). Peking University International Hospital (Shuang Liu); Peking Union Medical College Hospital (Juhong Shi); the First Affiliated Hospital of Chongqing Medical University (Hong Chen); the First Affiliated Hospital of Dalian Medical University (Yingqun Ji); the First Affiliated Hospital of Guangzhou Medical University (Chunli Liu); Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology (Xiansheng Liu); the Second Hospital of Jilin University (Chunling Dong); the First Medical Center of Chinese PLA General Hospital (Weihua Zhang); Tangdu Hospital of Air Force Military Medical University (Ning Wang); Affiliated Hospital of Nantong University (Songshi Ni); the Affiliated Hospital of Qingdao University (Zhaozhong Cheng); Shandong Provincial Hospital (Ling Zhu); Ruijin Hospital Affiliated to Shanghai Jiao Tong University (Guochao Shi); Central Hospital Affiliated to Shenyang Medical College (Shuyue Xia); Shenzhen People's Hospital (Yingyun Fu); Beijing Chao-yang Hospital of Capital Medical University (Yuanhua Yang); West China Hospital of Sichuan University (Qun Yi); Shanghai Pulmonary Hospital Affiliated to Tongji University (Jinming Liu); the First Affiliated Hospital of Zhengzhou University (Jianjun Jin); Fuwai Hospital of CAMS and PUMC (Changming Xiong and Zhihong Liu); Xiangya Hospital of Central South University (Yongjun Tang); and China-Japan Friendship Hospital (Jun Wan, Wanmu Xie, Qian Gao, Yihong Sun, and Zhenguo Zhai). Beijing Hospital (Jing Wang); the First Affiliated Hospital of Chongqing Medical University (Yuliang Liu and Xiaohui Wang); Affiliated Hospital of Jianghan University (Qin Wei); Evidence-based Medicine Center of School of Basic Medical Sciences of Lanzhou University (Xuan Yu and Xufei Luo); Beijing Anzhen Hospital of Capital Medical University (Meng Zhang); and China-Japan Friendship Hospital (Kaiyuan Zhen and Zhu Zhang). General Hospital of Northern Theater Command (Lei Liu and Po Zhang); Peking University Third Hospital (Jing Zhang); Beijing Jishuitan Hospital (Yunjian Zhang); Beijing Hospital (Baomin Fang and Yongjun Li); the First Affiliated Hospital of Bengbu Medical College (Qixia Xu); Institute of Respiratory Diseases of Changsha Medical University (Aiguo Dai); the First Affiliated Hospital of Dalian Medical University (Zhonghe Zhang); the Second Affiliated Hospital of the Third Military Medical University (Ye Fan); Dongguan People's Hospital (Ruhong Xu); the First Affiliated Hospital of Fujian Medical University (Chaosheng Deng); Dongguan People's Hospital (Ping Zhang); State Key Laboratory of Respiratory Diseases of National Clinical Research Center for Respiratory Disease of Guangzhou Institute of Respiratory Health of the First Affiliated Hospital of Guangzhou Medical University (Cheng Hong, Jian Wang, and Nuofu Zhang); Guizhou Provincial People's Hospital (Weijia Liu); the First Affiliated Hospital of Henan University of Science and Technology (Yimin Mao); Key Laboratory of Respiratory Diseases of the Ministry of Health of the Department of Pathophysiology of Tongji Medical College of Huazhong University of Science and Technology (Qinghua Hu); Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology (Guohua Zhen); the Second Hospital of Jilin University (Wei Xu); the Sixth Medical Center of PLA General Hospital (Yuying Li); Yan'an Hospital Affiliated to Kunming Medical University (Xiqian Xing); the First Affiliated Hospital with Nanjing Medical University (Weiping Xie); Inner Mongolia Baogang Hospital (Xiyuan Xu); Inner Mongolia People's Hospital (Jialie Wang); Shanxi Provincial People's Hospital (Aizhen Zhang); the First Hospital of Shanxi Medical University (Xiaoyun Hu and Yiwei Shi); Beijing Anzhen Hospital of Capital Medical University (Guangfa Zhu); Sichuan Provincial People's Hospital (Lu Guo); Tianjin Haihe Hospital (Qi Wu); Tianjin Medical University General Hospital (Jianlong Men and Lixia Dong); the First Affiliated Hospital of Wenzhou Medical University (Liangxing Wang); the First Affiliated Hospital of Xi'an Jiaotong University (Manxiang Li); Second People's Hospital of Tibet Autonomous Region (Wa Da); the People's Hospital of Xinjiang Uygur Autonomous Region (Ying Chen); Traditional Chinese Medicine Hospital of Xinjiang Uygur Autonomous Region (Huiqin Yang); the First Affiliated Hospital of Xinjiang Medical University (Hui Liu); Tumor Hospital Affiliated to Xinjiang Medical University (Qin Luo); Sir Run Run Shaw Hospital Affiliated to School of Medicine of Zhejiang University (Ruifeng Zhang and Kejing Ying); the First Hospital of China Medical University (Fan Liu); and Fuwai Hospital of CAMS and PUMC (Zhihong Liu). The present consensus statement was based on its Chinese version which has been published previously in the National Medical Journal of China, 2020 March, 100(11):808–813. DOI: 10.3760/cma.j.cn112137-20200209-00227, with full permission from the journal office and the above academic groups. ^* Drs. Zhai, Li, Chen, and Elalamy contributed equally to the manuscript.

Historically, the vaccination strategies developed in the second half of the 20th century have facilitated the eradication of infectious diseases. From the onset of COVID-19 pandemic to the end of April 2021, more than 150 million cases and 3 million deaths were documented worldwide with disruption of the economic and social activity, and with devastating material, physical, and psychological consequences. Reports of unusual and severe thrombotic events, including cerebral and splanchnic venous thrombosis and other autoimmune adverse reactions, such as immune thrombocytopenia or thrombotic microangiopathies in connection with some of the SARS-CoV-2 vaccines, have caused a great deal of concern within the population and the medical community. This report is intended to provide practical answers following an overview of our knowledge on these thrombotic events that are extremely rare but have serious consequences. Vaccine hesitancy threatens to reverse the progress made in controlling vaccine-preventable diseases. These adverse events must be put into perspective with an objective analysis of the facts and the issues of the vaccination strategy during this SARS-CoV-2 pandemic. Health care professionals remain the most pertinent advisors and influencers regarding vaccination decisions; they have to be supported to provide reliable and credible information on vaccines. We need to inform, reassure, and support our patients when the prescription is made. Facing these challenges and observations, a panel of experts express their insights and propose a tracking algorithm for vaccinated patients based on a 10-point guideline for decision-making on what to do and not to do.

Unlike classic APS, CAPS causes multiple microthrombosis due to an increased inflammatory response, known as a “thrombotic storm”. CAPS typically develops after infection, trauma, or surgery and begins with the following symptoms: fever, thrombocytopenia, muscle weakness, visual and cognitive disturbances, abdominal pain, renal failure, and disseminated intravascular coagulation. Although the presence of antiphospholipid antibodies in the blood is one of the diagnostic criteria, the level of these antibodies can fluctuate significantly, which complicates the diagnostic process and can lead to erroneous interpretation of rapidly developing symptoms. Triple therapy is often used to treat CAPS, which includes the use of anticoagulants, plasmapheresis, and high doses of glucocorticosteroids and, in some cases, additional intravenous immunoglobulins. The use of LMWH is recommended as the drug of choice due to its anti-inflammatory and anticoagulant properties. CAPS is a multifactorial disease that requires not only an interdisciplinary approach but also highly qualified medical care, adequate and timely diagnosis, and appropriate prevention in the context of relapse or occurrence of the disease. Improved new clinical protocols and education of medical personnel regarding CAPS can significantly improve the therapeutic approach and reduce mortality rates.

Newborns are the most vulnerable patients for thrombosis development among all children, with critically ill and premature infants being in the highest risk group. The upward trend in the rate of neonatal thrombosis could be attributed to progress in the treatment of severe neonatal conditions and the increased survival in premature babies. There are physiological differences in the hemostatic system between neonates and adults. Neonates differ in concentrations and rate of synthesis of most coagulation factors, turnover rates, the ability to regulate thrombin and plasmin, and in greater variability compared to adults. Natural inhibitors of coagulation (protein C, protein S, antithrombin, heparin cofactor II) and vitamin K-dependent coagulation factors (factors II, VII, IX, X) are low, but factor VIII and von Willebrand factor are elevated. Newborns have decreased fibrinolytic activity. In the healthy neonate, the balance is maintained but appears more easily converted into thrombosis. Neonatal hemostasis has less buffer capacity, and almost 95% of thrombosis is provoked. Different triggering risk factors are responsible for thrombosis in neonates, but the most important risk factors for thrombosis are central catheters, fluid fluctuations, liver dysfunction, and septic and inflammatory conditions. Low-molecular-weight heparins are the agents of choice for anticoagulation.