Distinctions between survivors and non-survivors with SARS-CoV-2 vaccine-induced thrombotic thrombocytopenia: A systematic review and meta-analysis

UNLABELLED: Vaccine-inducing immune thrombocytopenia, thrombosis, and bleeding emerge as infrequent and potential complications with mortality risk in healthy subjects. However, differences between survivors and non-survivors with SARS-CoV-2 vaccine-induced thrombotic thrombocytopenia (VITT) are unclear. METHODS: According to the PRISMA statement, we conducted a systematic review and meta-analysis, and the protocol was registered in PROSPERO. The main objective is to identify differences among survivors and non-survivors of SARS-CoV-2 VITT patients. We systematically searched through PubMed, Scopus, and Web of Science. We included cohorts, case series, and case reports. We classified bleeding complications according to the ISTH definition. Statistics: unpaired Student's t-test or one-way ANOVA, Wilcoxon, and Kruskal-Wallis. RESULTS: We systematically searched from January 2021 to June 2021 and identified 51 studies that included 191 patients. Non-survivors had the most severe thrombocytopenia (p 0.02) and lower fibrinogen measurements (p 0.01). Subjects vaccinated with mRNA vaccines (BNT162b2 and mRNA-1273) had an earlier onset of adverse events following immunization (p 0.001). We identified a higher trend of overall thrombotic events (p 0.001) in recipients of viral mechanism-dependent vaccines (Table 2). Non-survivors with cerebral venous sinus thrombosis (CVST) had more severe thrombocytopenia (p 0.01) than survivors with CVST. Finally, 61 % of survivors and 50 % with thrombosis received heparin. CONCLUSION: We identified more severe thrombocytopenia, lower fibrinogen measurements, and a higher trend of overall thrombotic events, including CVST and thrombotic storm, particularly with viral mechanisms-dependent vaccines in non-survivors VITT patients.