Population-wide persistent hemostatic changes after vaccination with ChAdOx1-S.

Area of Science:

• Hematology
• Immunology
• Vaccinology

Background:

• Reports suggest a potential link between anti-SARS-CoV-2 vaccines, including ChAdOx1-S, and an increased risk of thrombosis.
• Understanding the hemostatic and immune changes post-vaccination is crucial for assessing vaccine safety.

Purpose of the Study:

• To investigate the hemostatic and immune system changes following ChAdOx1-S vaccination.
• To evaluate potential mechanisms linking ChAdOx1-S vaccination to thrombotic events.

Main Methods:

• Blood samples from 631 health care workers were analyzed post-second ChAdOx1-S vaccination.
• Assessed hemostatic markers (D-dimer, fibrinogen, thrombin generation), endothelial function (VWF, active VWF), and immune markers (IL-6, IL-10).
• SARS-CoV-2 antibody titers were also determined.

Main Results:

• Vaccinated subjects showed reduced prothrombin and fibrinogen levels but higher prevalence outside normal ranges for prothrombin and antithrombin.
• Thrombin generation analysis revealed a more procoagulant profile with shortened lag time and time-to-peak, and increased peak height.
• Increased Von Willebrand Factor (VWF) and active VWF indicated endothelial activation, alongside significantly elevated IL-10 levels.

Conclusions:

• ChAdOx1-S vaccination is associated with significant alterations in hemostasis, including a procoagulant profile and endothelial activation.
• Persistently increased IL-10 suggests ongoing immune system activity post-vaccination, potentially contributing to thrombotic risk.
• These findings highlight a possible pathophysiological mechanism for increased thrombotic events after ChAdOx1-S vaccination.