Causal association between COVID-19 vaccination and thrombosis-related biomarkers/thrombosis/ischemic stroke: Mendelian randomization study

Background: Observational studies about the association between coronavirus disease 2019 (COVID-19) vaccination and thrombosis/ischemic stroke are inconsistent. The aim of this study is to assess the causality between COVID-19 vaccination and thrombosis-related biomarkers/thrombosis/ischemic stroke using mendelian randomization (MR) analysis. Methods: A two-sample MR analysis using publicly available genome-wide association study (GWAS) data was conducted. Causal effects were appraised using inverse variance weighted (IVW, as a primary method), with supplementary methods including constrained maximum likelihood and model averaging, MR-Robust Adjusted Profile Score, MR-Egger regression, simple mode, weighted median, and weighted mode. Sensitivity analyses were conducted using Cochran's Q test, MR-Egger intercept test, and leave-one-out analysis. Results: Genetically predicted COVID-19 vaccination was negatively associated with C-C motif chemokine 3 [CCL3, odds ratio (OR): 0.694, 95% confidence intervals (CI): 0.484-0.995] and multiple coagulation factor deficiency protein 2 (MCFD2, OR: 0.806, 95% CI: 0.675-0.963). Meanwhile, the IVW analysis revealed significant causal effects between genetically predicted COVID-19 vaccination and ischemic stroke (OR: 1.088, 95% CI: 1.006-1.177), large artery stroke (LAS, OR: 1.251, 95% CI: 1.028-1.521). The leave-one-out analysis revealed that no individual SNP exerted a significant effect on the overall causal estimate. Conclusion: Our study provided evidence supporting a potential causal association of genetically predicted COVID-19 vaccination with CCL3 levels, MCFD2 levels, ischemic stroke risk and LAS risk. These results provide preliminary evidence of potential adverse associations, but further studies are required to fully understand the mechanisms and to validate these findings across broader populations.