ChAdOx1 vaccination, blood coagulation, and inflammation: No effect on coagulation but increased interleukin‐6

BACKGROUND: Vaccination is the leading approach in combatting the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic. ChAdOx1 nCoV‐19 vaccination (ChAdOx1) has been linked to a higher frequency of rare thrombosis and thromboembolism. This study aimed to explore markers related to the blood coagulation system activation and inflammation, before and after ChAdOx1 vaccination. PATIENTS AND METHODS: An observational cohort study including 40 health care workers. Whole blood samples were collected before, and either 1 or 2 days after vaccination. Activated coagulation factors in complex with their natural inhibitors were determined by custom ELISAs, including thrombin:antithrombin (T:AT), kallikrein:C1‐esterase‐inhibitor (PKa:C1Inh), factor(F)IXa:AT, FXa:AT, FXIaAT, FXIa:alpha‐1‐antitrypsin (α1AT), FXIa:C1inh, and FVIIa:AT. Plasma concentrations of interleukin (IL)‐6 and IL‐18 were quantified via ELISA. Analyses were performed using Wilcoxon signed‐rank test. RESULTS: Levels of FVIIa:AT decreased with a median (IQR) of 707 (549–1028) pg/ml versus 598 (471–996) pg/ml, p = 0.01; and levels of IL‐6 increased, 4.0 (1.9–6.8) pg/ml versus 6.9 (3.6–12.2) pg/ml, p = 0.02, after vaccination. No changes were observed in T:AT, PKa:C1Inh, FIXa:AT, FXa:AT, FXIaAT, FXIa:α1AT, FXIa:C1inh, and IL‐18. CONCLUSION: ChAdOx1 leads to an inflammatory response with increased levels of IL‐6. We did not observe activation of the blood coagulation system 1–2 days following vaccination.