PB0070 - Vaccine Induced Thrombotic Thrombocytopenia post Dose 2 ChAdOx1 nCoV19 vaccination: less severe but not void of catastrophic outcomes

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Co-Author(s)

LC

Lisa Clarke

Consultant Haematologist
Department of Haematology, Concord Repatriation General Hospital; Australian Red Cross Lifeblood, Sydney Adventist Hospital
Concord, New South Wales, Australia
HT

Huyen Tran

Professor
Australian Centre for Blood Diseases, Monash University
Melbourne, Victoria, Australia
JC

Jennifer Curnow

Consultant Haematologist
Director Clinical Haematology WSLHD, Senior Staff Specialist, Westmead hospital Director Westmead Haemophilia Treatment Centre Clinical Assoc. Professor in Discipline of Medicine, Faculty of Medicine and Health, University of Sydney
Westmead, New South Wales, Australia
JF

Julianne Falconer

Haemostasis and Thrombosis Fellow
Concord Repatriation General Hospital
Concord, New South Wales, Australia
SC

Sanjeev Chunilal

Haematologist
Monash Health
Melbourne, Victoria, Australia
TB

Timothy Brighton

Professor
Prince of Wales Hospital
Sydney, New South Wales, Australia
FP

Freda Passam

Group Leader
Haematology Research Group, Charles Perkins Centre, University of Sydney
Sydney, New South Wales, Australia

Presenting Author(s)

Christine S M Lee, PhD

Postdoctoral Research Fellow
ANZAC Research Institute, University of Sydney
Sydney, New South Wales, Australia

Co-Author(s)

DD

Dea Donikian

Hospital Scientist
Department Haematology, New South Wales Health Pathology, Prince of Wales Hospital
Sydney, New South Wales, Australia
MK

Mayuko Kondo

Hospital Scientist
Department Haematology, New South Wales Health Pathology, Prince of Wales Hospital
Sydney, New South Wales, Australia
VC

Vivien M. Chen, Phd FRACP FRCPA

Group Leader, Staff Specialist Haematologist
ANZAC Research Institute, University of Sydney
Sydney, New South Wales, Australia

Background: Clinical and pathological features of vaccine induced immune thrombotic thrombocytopenia (VITT) following first dose ChAdOx1 nCoV19 vaccination (AZD1222) are well described. VITT post 2nd dose AZD1222 is not widely recognised however its plausible undiagnosed platelet activating antibodies formed after dose 1 may be boosted upon subsequent exposure. (Greinacher et al).

Aims: We describe the clinicopathological features of suspected VITT post 2nd dose AZD1222 in Australia.

Methods: We conducted a prospective cohort study capturing sequential requests for confirmatory testing for suspected VITT after 2nd dose AZD1222. Testing was based upon key clinicopathological features: thrombosis within timeframe (4-42 days), thrombocytopenia, D-Dimer >5xULN. High probability VITT (all criteria) underwent immunoassay Asserachrom HPIA IgG (Diagnostica Stago) and functional assay (serotonin release assay or procoagulant flow cytometry). Confirmed VITT cases were compared with those presenting after first dose AZD1222.
Descriptive and comparative statistics were performed using SAS studio version 9.4.

Results: 35 high probability VITT cases presented at a median of 14days (IQR 9,18) post 2nd dose with platelet count 116 x109/L (IQR 92, 139) and 14.5 fold increase in D-dimer (IQR 9.4,28.8) were tested. Median dose interval was 84days (range 25-100), age 70years (IQR 62, 78) with a male predominance of 66%. Platelet count and D-dimer fold change were less severe compared to cases post 1st dose (Table 1).
PF4 antibodies by ELISA were detected in 4 (11%) and antibody mediated platelet activation demonstrable in 19 (54%). These cases were classified as confirmed VITT.
Three catastrophic cases including 2 fatalities occurred (Graph 2). Concomitant factors were present in all and influenced outcome severity.

Conclusion(s): We describe the largest cohort of suspected VITT post 2nd dose AZD1222. Confirmed cases are similar to those post D1 but platelet count and D-Dimer changes were milder. Similarly, catastrophic cases occurred however concomitant factors were present in all including shorter dosing intervals.