Thrombotic and Thromboembolic Complications After Vaccination Against COVID-19: A Systematic Review

Thromboembolic complications after the COVID-19 vaccination have been reported from all over the world. We aimed to identify the thrombotic and thromboembolic complications that can arise after receiving various types of COVID-19 vaccines, their frequency, and distinguishing characteristics. Articles published in Medline/PubMed, Scopus, EMBASE, Google Scholar, EBSCO, Web of Science, the Cochrane Library, the CDC database, the WHO database, ClinicalTrials.gov, and servers like medRxiv.org and bioRxiv.org, as well as the websites of several reporting authorities between December 1, 2019, and July 29, 2021, were searched. Studies were included if they reported any thromboembolic complications post-COVID-19 vaccination and excluded editorials, systematic reviews, meta-analyses, narrative reviews, and commentaries. Two reviewers independently extracted the data and conducted the quality assessment. Thromboembolic events and associated hemorrhagic complications after various types of COVID-19 vaccines, their frequency, and distinguishing characteristics were assessed. The protocol was registered at PROSPERO (ID-CRD42021257862). There were 59 articles, enrolling 202 patients. We also studied data from two nationwide registries and surveillance. The mean age of presentation was 47 ± 15.5 (mean ± SD) years, and 71.1% of the reported cases were females. The majority of events were with the AstraZeneca vaccine and with the first dose. Of these, 74.8% were venous thromboembolic events, 12.7% were arterial thromboembolic events, and the rest were hemorrhagic complications. The most common reported event was cerebral venous sinus thrombosis (65.8%), followed by pulmonary embolism, splanchnic vein thrombosis, deep vein thrombosis, and ischemic and hemorrhagic stroke. The majority had thrombocytopenia, high D-dimer, and anti-PF4 antibodies. The case fatality rate was 26.5%. In our study, 26/59 of the papers were of fair quality. The data from two nationwide registries and surveillance revealed 6347 venous and arterial thromboembolic events post-COVID-19 vaccinations. COVID-19 vaccinations have been linked to thrombotic and thromboembolic complications. However, the benefits far outweigh the risks. Clinicians should be aware of these complications because they may be fatal and because prompt identification and treatment can prevent fatalities.