. 2022 Oct 17;21(2):176–184. doi: 10.2450/2022.0060-22

Table I.

Studies on thrombotic risk in recipients of COVID-19 vaccines

First author, Journal^Ref Type of study	Date of publication	Vaccine	CSVT	TTS	Other information
Pottegard A, BMJ ¹² Population-based	May 2021	Viral vectored	Morbidity ratio 20.25 (8.14–41.73)	Morbidity ratio for any thrombocytopenia/coagulation disorders 1.52 (0.97 to 2.25)	Morbidity ratio for arterial events: 0.97 (95% CI 0.77–1.20) Morbidity ratio for VTE: 1.97 (1.50–2.54)
Bikdeli B, 2021, JAMA ¹¹ Surveillance	July 2021	Viral vectored	3.6 (99% CI: 2.7–4.8) per million recipients	n.a.	MHRA No sex-disaggregated data
Simpson CR Nat Med ¹⁶ Population-based (with nested-incident matched case-control and self-controlled case-series analysis)	July 2021	Viral vectored and m-RNA	Not informative data	n.a.	No association with VTE for both types of vaccines Arterial events in viral vectored vaccine recipients aRR 1.48 (95% CI 1.12–1.96)
Cari L J Autoimm ¹³ Eudra Vigilance European database	August 2021	Viral vectored and m-RNA	Increase of SAE rate in subjects 18–64-years vs >64 years: mean (95% CI) Viral vector recipients 5.7 (5.1–6.2) mRNA recipients 2.0 (1.7–2.3)	Increase of SAE rate in subjects 18–64 years vs >64 years: mean (95% CI) Viral vectored recipients 2.5 (2.3–2.7) mRNA recipients 1.9 (1.6–2.2)	Splanchnic vein thromboses increase of SAE rate in subjects 18–64 years vs >64 years: mean (95% CI) Viral vectored recipients 4.0 (3.7–4.3) mRNA recipients 2.1 (1.8–2.4) Sex-disaggregated raw data (see Figures 2, 3 and 4)
Palaiodimou L, Neurology ⁹ Systematic review	October 2021	Viral vectored	370 patients (69 studies) Women proportion pooled estimate 75% (95% CI 69–80%) 28% of those with post-vaccination CVST died during hospitalization (pooled rate 28%; 95% CI 21–36%; 14 studies)	72 patients (12 studies) TTS was independently associated with a higher likelihood of CVST when compared to patients without TTS with thrombotic events after vaccination (OR 13.8; 95% CI 2.0–97.3) Women with TTS-CSVT proportion pooled estimate 75% (95% CI 69–81) Women with any TTS 71% (95% CI 62–80%)	All venous and arterial thromboses were eligible. Women among patients with any thrombotic event, 69% (95% CI 60–77%)
Hafeez MU, Clin Appl Thromb Hemost ¹⁰ Systematic review	October 2021	Viral vectored and m-RNA	n.a.	59 studies F/M: 51/18 63 out of 69 (91.3%) occurred after viral vector vaccine
Klein NP, JAMA ¹⁴ Surveillance	October 2021	m-RNA	Excess cases in risk interval 0.2 (−1.1 to 0.5) per million doses	Excess cases in risk interval 1.0 (−4.6 to 1.4) per million doses	MHRA No sex-disaggregated data
Uaprasert N, Thromb J ²⁸ Systematic review and meta-analysis	November 2021	Viral vector ed and m-RNA	n.a.	n.a.	8 RCTs included No increased risk of thromboembolism, and death from thromboembolism. No sex-disaggregated data

CI: confidence interval; MHRA: Medicines and Healthcare Products Regulatory Agency; aRR: adjusted relative risk; VTE: venous thromboembolism; RCT: randomized controlled trials; TTS: thrombosis and thrombocytopenia syndrome; n.a.: not applicable.