ABSTRACT
Background: Inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC), is associated with higher thrombotic risk and enhanced thrombin generation (TG) in adults. IBD patients were underrepresented in SARS-CoV- 2 mRNA vaccine trials. Case reports indicated that adverse events post-vaccination, including IBD flare, were more common among children, and those with prior COVID-19. Aim(s): To find out whether TG is increased in children with IBD as compared to healthy controls and whether TG parameters show significant changes following SARS-CoV- 2 mRNA vaccination. Method(s): In this observational case-control study, 37 children with IBD (CD:16, UC: 21) aged 12-18 years and 55 healthy age-matched children were enrolled. Blood was collected before and 2-4 weeks after the second dose of BNT162b2 (Pfizer-BioNTech) vaccine dose. Whole blood count, fibrinogen, inflammatory markers (CRP, ferritin), anti-SARS- CoV- 2 antibody levels were investigated, TG assay was carried-out using platelet-poor plasma. Lag time, endogen thrombin potential (ETP), peak thrombin, time-to- peak were calculated. Detailed clinical parameters including post-vaccination symptoms, COVID-19 history, disease activity scores (PUCAI, Mayo score, PCDAI) were registered. Result(s): CRP was significantly elevated in children with IBD and showed a positive correlation with ETP (CD: R = 0.700;p = 0.003 and CU: R = 0.501;p = 0.020). TG parameters did not differ between patients and controls pre-or post-vaccination. TG parameters remained unaltered post-vaccination in both groups. IBD disease flare was not observed post-vaccination, but reduced anti-SARS- CoV- 2 antibody titers were found in 4 patients receiving immunosuppressive therapies. Previous COVID-19 infection had no effect on TG levels. Conclusion(s): Although TG parameters correlated with the level of inflammation in children with IBD, the extent of TG was not significantly different from healthy controls. TG parameters and IBD disease activity scores did not increase significantly following mRNA vaccination. Our results support the safety of SARS-CoV- 2 mRNA vaccination in children with IBD, highlighting observations of lower antibody titers in immunosuppressed children.