Reactions 1871, p8 - 4 Sep 2021AstraZeneca COVID-19 vaccine-related thrombocytopenia and thrombosis

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Reactions 1871, p8 - 4 Sep 2021

AstraZeneca COVID-19 vaccine-related thrombocytopenia and thrombosis

The likelihood of death due to AstraZeneca COVID-19 vaccine [AZD-1222; ChAdOx1-S]-related immune thrombocytopenia and thrombosis (VITT) is greatest in patients with a low platelet count and cerebral haemorrhage, according to findings of a prospective cohort study published in the New England Journal of Medicine.

An expert haematology panel conducted a study in all patients with suspected VITT reported at National Health Service hospitals between 22 March 2021 and 6 June 2021 to investigate VTTT risk factors, treatment and mortality.

Definite VTTT was defined as: onset of symptoms 5–30 days after COVID-19, thrombosis, thrombocytopenia (platelet count <150 000/mm³), d-dimer level >4000 fibrinogen-equivalent units (FEUs), and antibodies to platelet factor 4.

Of 294 cases evaluated, 170 and 50 were classified having definite and probable VITT, respectively. Patients presented to hospital 5-48 (median 14) days after vaccination with the Oxford–AstraZeneca COVID-19 vaccine, and were 18–79 years of age. No medical risk factors were identified.

Overall, 50% of patients with definite or probable VITT had cerebral venous sinus thrombosis, and 36% of these patients also had cerebral haemorrhage.

The overall death rate was 22%. The risk of death was significantly increased in patients with cerebral venous sinus thrombosis (odds ratio 2.7; 95% CI 1.4, 5.2), and for every 50% decrease in baseline platelet count, for every increase of 10 000 FEUs in baseline d-dimer level, for every 50% decrease in the baseline fibrinogen level. Multivariate analysis found that baseline platelet count and cerebral haemorrhage were independently associated with death; the mortality was 73% in patients with platelet counts less than 30 000/mm³ and cerebral haemorrhage.

"We did not find any individual risk factors for VITT, but we found increased mortality among patients who presented with severe thrombocytopenia, cerebral venous sinus thrombosis, intracranial hemorrhage, laboratory markers of severe coagulation activation, or all these variables. In our cohort, the cases of VITT were associated only with the first ChAdOx1 nCoV-19 vaccination, and VITT primarily affected patients younger than 60 years of age," said the authors.

Pavord S, et al. Clinical Features of Vaccine-Induced Immune Thrombocytopenia and Thrombosis. New England Journal of Medicine : 11 Aug 2021. Available from: URL:

http://doi.org/10.1056/NEJMoa2109908 803590462