Risk of thrombocytopenic, haemorrhagic and thromboembolic disorders following COVID-19 vaccination and positive test: a self-controlled case series analysis in Wales

There is a need for better understanding of the risk of thrombocytopenic, haemorrhagic, thromboembolic disorders following first, second and booster vaccination doses and testing positive for SARS-CoV-2. Self-controlled cases series analysis of 2.1 million linked patient records in Wales between 7th December 2020 and 31st December 2021. Outcomes were the first diagnosis of thrombocytopenic, haemorrhagic and thromboembolic events in primary or secondary care datasets, exposure was defined as 0–28 days post-vaccination or a positive reverse transcription polymerase chain reaction test for SARS-CoV-2. 36,136 individuals experienced either a thrombocytopenic, haemorrhagic or thromboembolic event during the study period. Relative to baseline, our observations show greater risk of outcomes in the periods post-first dose of BNT162b2 for haemorrhagic (IRR 1.47, 95%CI: 1.04–2.08) and idiopathic thrombocytopenic purpura (IRR 2.80, 95%CI: 1.21–6.49) events; post-second dose of ChAdOx1 for arterial thrombosis (IRR 1.14, 95%CI: 1.01–1.29); post-booster greater risk of venous thromboembolic (VTE) (IRR-Moderna 3.62, 95%CI: 0.99–13.17) (IRR-BNT162b2 1.39, 95%CI: 1.04–1.87) and arterial thrombosis (IRR-Moderna 3.14, 95%CI: 1.14–8.64) (IRR-BNT162b2 1.34, 95%CI: 1.15–1.58). Similarly, post SARS-CoV-2 infection the risk was increased for haemorrhagic (IRR 1.49, 95%CI: 1.15–1.92), VTE (IRR 5.63, 95%CI: 4.91, 6.4), arterial thrombosis (IRR 2.46, 95%CI: 2.22–2.71). We found that there was a measurable risk of thrombocytopenic, haemorrhagic, thromboembolic events after COVID-19 vaccination and infection.

Author list



  1. Population Data Science, Faculty of Medicine, Health & Life Science, Swansea University Medical School, Swansea University, Swansea, Wales, UK. 
  2. Centre for Public Health, School of Medicine Dentistry and Biomedical Sciences, Queen’s University Belfast, Belfast, UK.
  3. Public Health Agency, Belfast, UK. 
  4. School of Medicine, University of St Andrews, St Andrews, UK. 
  5. Institute of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK. 
  6. PPI, HDR UK BREATHE Hub, Edinburgh, UK. 
  7. Vaccine Preventable Disease Programme, Public Health Wales, Cardiff, UK. 
  8. Usher Institute, University of Edinburgh, Edinburgh, UK. 
  9. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK. 
  10. Department of Mathematics and Statistics, Strathclyde University, Glasgow and Public Health Scotland, Glasgow, UK.
  11. School of Health, Victoria University of Wellington, Wellington, New Zealand. 
  12. HDR UK BREATHE Hub, Usher Institute, University of Edinburgh, Edinburgh, UK.


Fatemeh Torabi1*, Stuart Bedston1, Emily Lowthian1, Ashley Akbari1, Rhiannon K. Owen1, Declan T. Bradley2,3, Utkarsh Agrawal4, Peter Collins5, Richard Fry1, Lucy J. Griffiths1, Jillian Beggs6, Gareth Davies1, Joe Hollinghurst1, Jane Lyons1, Hoda Abbasizanjani1, Simon Cottrell7, Malorie Perry7, Richard Roberts7, Amaya Azcoaga‐Lorenzo4, Adeniyi Francis Fagbamigbe4, Ting Shi8, Ruby S. M. Tsang9, Chris Robertson10, F. D. Richard Hobbs9, Simon de Lusignan9, Colin McCowan4, Michael Gravenor1, Colin R. Simpson8,11, Aziz Sheikh12,13 & Ronan A. Lyons1,13

Novel Coronavirus SARS-CoV-2


Nature - Scientific Reports