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Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study.
BMJ. 2021 08 26; 374:n1931.BMJ

Abstract

OBJECTIVE

To assess the association between covid-19 vaccines and risk of thrombocytopenia and thromboembolic events in England among adults.

DESIGN

Self-controlled case series study using national data on covid-19 vaccination and hospital admissions.

SETTING

Patient level data were obtained for approximately 30 million people vaccinated in England between 1 December 2020 and 24 April 2021. Electronic health records were linked with death data from the Office for National Statistics, SARS-CoV-2 positive test data, and hospital admission data from the United Kingdom's health service (NHS).

PARTICIPANTS

29 121 633 people were vaccinated with first doses (19 608 008 with Oxford-AstraZeneca (ChAdOx1 nCoV-19) and 9 513 625 with Pfizer-BioNTech (BNT162b2 mRNA)) and 1 758 095 people had a positive SARS-CoV-2 test. People aged ≥16 years who had first doses of the ChAdOx1 nCoV-19 or BNT162b2 mRNA vaccines and any outcome of interest were included in the study.

MAIN OUTCOME MEASURES

The primary outcomes were hospital admission or death associated with thrombocytopenia, venous thromboembolism, and arterial thromboembolism within 28 days of three exposures: first dose of the ChAdOx1 nCoV-19 vaccine; first dose of the BNT162b2 mRNA vaccine; and a SARS-CoV-2 positive test. Secondary outcomes were subsets of the primary outcomes: cerebral venous sinus thrombosis (CVST), ischaemic stroke, myocardial infarction, and other rare arterial thrombotic events.

RESULTS

The study found increased risk of thrombocytopenia after ChAdOx1 nCoV-19 vaccination (incidence rate ratio 1.33, 95% confidence interval 1.19 to 1.47 at 8-14 days) and after a positive SARS-CoV-2 test (5.27, 4.34 to 6.40 at 8-14 days); increased risk of venous thromboembolism after ChAdOx1 nCoV-19 vaccination (1.10, 1.02 to 1.18 at 8-14 days) and after SARS-CoV-2 infection (13.86, 12.76 to 15.05 at 8-14 days); and increased risk of arterial thromboembolism after BNT162b2 mRNA vaccination (1.06, 1.01 to 1.10 at 15-21 days) and after SARS-CoV-2 infection (2.02, 1.82 to 2.24 at 15-21 days). Secondary analyses found increased risk of CVST after ChAdOx1 nCoV-19 vaccination (4.01, 2.08 to 7.71 at 8-14 days), after BNT162b2 mRNA vaccination (3.58, 1.39 to 9.27 at 15-21 days), and after a positive SARS-CoV-2 test; increased risk of ischaemic stroke after BNT162b2 mRNA vaccination (1.12, 1.04 to 1.20 at 15-21 days) and after a positive SARS-CoV-2 test; and increased risk of other rare arterial thrombotic events after ChAdOx1 nCoV-19 vaccination (1.21, 1.02 to 1.43 at 8-14 days) and after a positive SARS-CoV-2 test.

CONCLUSION

Increased risks of haematological and vascular events that led to hospital admission or death were observed for short time intervals after first doses of the ChAdOx1 nCoV-19 and BNT162b2 mRNA vaccines. The risks of most of these events were substantially higher and more prolonged after SARS-CoV-2 infection than after vaccination in the same population.

Authors+Show Affiliations

Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK julia.hippisley-cox@phc.ox.ac.uk.Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK.Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK.Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK.Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK.Leicester Real World Evidence Unit, Leicester Diabetes Centre, University of Leicester, Leicester, UK.Leicester Real World Evidence Unit, Leicester Diabetes Centre, University of Leicester, Leicester, UK.Nuffield Department of Clinical Neurosciences, University of Oxford, NIHR Biomedical Research Centre, Oxford University Hospitals NHS Trust, Oxford, UK. Intensive Care National Audit & Research Centre, London, UK.Department of Critical Care Medicine, Guys and St Thomas' NHS Foundation Trust, London, UK.Intensive Care National Audit & Research Centre, London, UK. Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.Intensive Care National Audit & Research Centre, London, UK. Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK.Primary Care Unit, Department of Public Health and Primary Care, School of Clinical Medicine, University of Cambridge, Cambridge, UK. MRC Epidemiology Unit, Institute of Metabolic Science, School of Clinical Medicine, University of Cambridge, Cambridge, UK.Usher Institute, University of Edinburgh, Edinburgh, UK.Nuffield Department of Primary Health Care Sciences, University of Oxford, Oxford, UK. Division of Primary Care, School of Medicine, University of Nottingham, Nottingham, UK.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

34446426

Citation

Hippisley-Cox, Julia, et al. "Risk of Thrombocytopenia and Thromboembolism After Covid-19 Vaccination and SARS-CoV-2 Positive Testing: Self-controlled Case Series Study." BMJ (Clinical Research Ed.), vol. 374, 2021, pp. n1931.
Hippisley-Cox J, Patone M, Mei XW, et al. Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study. BMJ. 2021;374:n1931.
Hippisley-Cox, J., Patone, M., Mei, X. W., Saatci, D., Dixon, S., Khunti, K., Zaccardi, F., Watkinson, P., Shankar-Hari, M., Doidge, J., Harrison, D. A., Griffin, S. J., Sheikh, A., & Coupland, C. A. C. (2021). Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study. BMJ (Clinical Research Ed.), 374, n1931. https://doi.org/10.1136/bmj.n1931
Hippisley-Cox J, et al. Risk of Thrombocytopenia and Thromboembolism After Covid-19 Vaccination and SARS-CoV-2 Positive Testing: Self-controlled Case Series Study. BMJ. 2021 08 26;374:n1931. PubMed PMID: 34446426.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study. AU - Hippisley-Cox,Julia, AU - Patone,Martina, AU - Mei,Xue W, AU - Saatci,Defne, AU - Dixon,Sharon, AU - Khunti,Kamlesh, AU - Zaccardi,Francesco, AU - Watkinson,Peter, AU - Shankar-Hari,Manu, AU - Doidge,James, AU - Harrison,David A, AU - Griffin,Simon J, AU - Sheikh,Aziz, AU - Coupland,Carol A C, Y1 - 2021/08/26/ PY - 2021/8/27/entrez PY - 2021/8/28/pubmed PY - 2021/9/9/medline SP - n1931 EP - n1931 JF - BMJ (Clinical research ed.) JO - BMJ VL - 374 N2 - OBJECTIVE: To assess the association between covid-19 vaccines and risk of thrombocytopenia and thromboembolic events in England among adults. DESIGN: Self-controlled case series study using national data on covid-19 vaccination and hospital admissions. SETTING: Patient level data were obtained for approximately 30 million people vaccinated in England between 1 December 2020 and 24 April 2021. Electronic health records were linked with death data from the Office for National Statistics, SARS-CoV-2 positive test data, and hospital admission data from the United Kingdom's health service (NHS). PARTICIPANTS: 29 121 633 people were vaccinated with first doses (19 608 008 with Oxford-AstraZeneca (ChAdOx1 nCoV-19) and 9 513 625 with Pfizer-BioNTech (BNT162b2 mRNA)) and 1 758 095 people had a positive SARS-CoV-2 test. People aged ≥16 years who had first doses of the ChAdOx1 nCoV-19 or BNT162b2 mRNA vaccines and any outcome of interest were included in the study. MAIN OUTCOME MEASURES: The primary outcomes were hospital admission or death associated with thrombocytopenia, venous thromboembolism, and arterial thromboembolism within 28 days of three exposures: first dose of the ChAdOx1 nCoV-19 vaccine; first dose of the BNT162b2 mRNA vaccine; and a SARS-CoV-2 positive test. Secondary outcomes were subsets of the primary outcomes: cerebral venous sinus thrombosis (CVST), ischaemic stroke, myocardial infarction, and other rare arterial thrombotic events. RESULTS: The study found increased risk of thrombocytopenia after ChAdOx1 nCoV-19 vaccination (incidence rate ratio 1.33, 95% confidence interval 1.19 to 1.47 at 8-14 days) and after a positive SARS-CoV-2 test (5.27, 4.34 to 6.40 at 8-14 days); increased risk of venous thromboembolism after ChAdOx1 nCoV-19 vaccination (1.10, 1.02 to 1.18 at 8-14 days) and after SARS-CoV-2 infection (13.86, 12.76 to 15.05 at 8-14 days); and increased risk of arterial thromboembolism after BNT162b2 mRNA vaccination (1.06, 1.01 to 1.10 at 15-21 days) and after SARS-CoV-2 infection (2.02, 1.82 to 2.24 at 15-21 days). Secondary analyses found increased risk of CVST after ChAdOx1 nCoV-19 vaccination (4.01, 2.08 to 7.71 at 8-14 days), after BNT162b2 mRNA vaccination (3.58, 1.39 to 9.27 at 15-21 days), and after a positive SARS-CoV-2 test; increased risk of ischaemic stroke after BNT162b2 mRNA vaccination (1.12, 1.04 to 1.20 at 15-21 days) and after a positive SARS-CoV-2 test; and increased risk of other rare arterial thrombotic events after ChAdOx1 nCoV-19 vaccination (1.21, 1.02 to 1.43 at 8-14 days) and after a positive SARS-CoV-2 test. CONCLUSION: Increased risks of haematological and vascular events that led to hospital admission or death were observed for short time intervals after first doses of the ChAdOx1 nCoV-19 and BNT162b2 mRNA vaccines. The risks of most of these events were substantially higher and more prolonged after SARS-CoV-2 infection than after vaccination in the same population. SN - 1756-1833 UR - https://www.unboundmedicine.com/medline/citation/34446426/Risk_of_thrombocytopenia_and_thromboembolism_after_covid_19_vaccination_and_SARS_CoV_2_positive_testing:_self_controlled_case_series_study_ L2 - http://www.bmj.com/lookup/pmidlookup?view=long&pmid=34446426 DB - PRIME DP - Unbound Medicine ER -