Seminars in thrombosis and hemostasisSep 29, 2022

Higher Blood Clotting in Beta and Delta COVID-19 Variants Compared to Milder Omicron Variants Linked to Clotting Test Results, Abnormal Clot Proteins, and Illness Severity

Updated Jan 20, 2026

Abstract

Clotting parameters associated with omicron variants are significantly raised compared to healthy controls but lower than those seen with more severe variants.

Omicron variants of SARS-CoV-2 are linked to increased clotting parameters compared to healthy individuals.
Clotting levels in omicron infections are significantly lower than those associated with more virulent variants like beta and delta.
Individuals infected with omicron variants show less extensive formation of fibrin amyloid microclots in platelet-poor plasma.
The differences in clotting effects among variants may help indicate the relationship between coagulopathy and variant virulence.
Microclots may be relevant in understanding the severity of symptoms in COVID-19.

Simplified

Earlier variants of SARS-CoV-2 have been associated with hypercoagulability and an extensive formation of fibrin amyloid microclots, which are considered to contribute to the pathology of the coronavirus 2019 disease (COVID-19). The newer omicron variants appear to be far more transmissible, but less virulent, even when taking immunity acquired from previous infections or vaccination into account. We here show that while the clotting parameters associated with omicron variants are significantly raised over those of healthy, matched controls, they are raised to levels significantly lower than those seen with more severe variants such as beta and delta. We also observed that individuals infected with omicron variants manifested less extensive microclot formation in platelet-poor plasma compared with those harboring the more virulent variants. The measurement of clotting effects between the different variants acts as a kind of "internal control" that demonstrates the relationship between the extent of coagulopathies and the virulence of the variant of interest. This adds to the evidence that microclots may play an important role in reflecting the severity of symptoms observed in COVID-19.

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Competing interests

M.J.K. is a nonexecutive director and shareholder of Gknowmix (Pty) Ltd. E.P. is the managing director of BioCODE Technologies. E.E.M., H.B.M., M.D.N. have received research grants from Haemonetics Corporation outside the submitted work. M.D.N. has received an honorarium from Haemonetics Corporation for speaking engagements, as well as research support from Janssen Pharmaceuticals (Beerse, Belgium) and Noveome Biotherapeutics (Pittsburgh, PA) outside the submitted work. He has served as a consultant to Janssen and CSL Behring (King of Prussia, PA) and serves on the Scientific Advisory Board of Haima Therapeutics (Cleveland, OH). M.M.W. has received honoraria from Alexion Pharmaceuticals (Boston, MA).

PubMed

Higher Blood Clotting in Beta and Delta COVID-19 Variants Compared to Milder Omicron Variants Linked to Clotting Test Results, Abnormal Clot Proteins, and Illness Severity

Abstract

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