Welcome to PracticeUpdate! We hope you are enjoying temporary access to this content.
Please register today for a free account and gain full access
to all of our expert-selected content.
Already Have An Account? Log in Now
First-Dose ChAdOx1 and BNT162b2 COVID-19 Vaccines and Thrombocytopenic, Thromboembolic, and Hemorrhagic Events
TAKE-HOME MESSAGE
-
The authors of this case–control study evaluated outcomes among individuals in Scotland with an incident event of immune thrombocytopenia (ITP), thromboembolism, or hemorrhage after the first dose of either the BNT162b2 or ChAdOx1 vaccine. There was an association between the ChAdOx1 vaccine and ITP, arterial thromboembolic events, and hemorrhagic events. However, confirmatory self-controlled case series analysis revealed an increased risk only for ITP after the ChAdOx1 vaccine. There were no associations between the occurrence of incident hematological events and the BNT162b2 vaccine.
- There is an increased risk for developing ITP after receiving the first dose of the ChAdOx1 vaccine and no risk for adverse hematological events in individuals who received the BNT162b2 vaccine.
abstract
This abstract is available on the publisher's site.
Access this abstract nowReports of ChAdOx1 vaccine–associated thrombocytopenia and vascular adverse events have led to some countries restricting its use. Using a national prospective cohort, we estimated associations between exposure to first-dose ChAdOx1 or BNT162b2 vaccination and hematological and vascular adverse events using a nested incident-matched case-control study and a confirmatory self-controlled case series (SCCS) analysis. An association was found between ChAdOx1 vaccination and idiopathic thrombocytopenic purpura (ITP) (0–27 d after vaccination; adjusted rate ratio (aRR) = 5.77, 95% confidence interval (CI), 2.41–13.83), with an estimated incidence of 1.13 (0.62–1.63) cases per 100,000 doses. An SCCS analysis confirmed that this was unlikely due to bias (RR = 1.98 (1.29–3.02)). There was also an increased risk for arterial thromboembolic events (aRR = 1.22, 1.12–1.34) 0–27 d after vaccination, with an SCCS RR of 0.97 (0.93–1.02). For hemorrhagic events 0–27 d after vaccination, the aRR was 1.48 (1.12–1.96), with an SCCS RR of 0.95 (0.82–1.11). A first dose of ChAdOx1 was found to be associated with small increased risks of ITP, with suggestive evidence of an increased risk of arterial thromboembolic and hemorrhagic events. The attenuation of effect found in the SCCS analysis means that there is the potential for overestimation of the reported results, which might indicate the presence of some residual confounding or confounding by indication. Public health authorities should inform their jurisdictions of these relatively small increased risks associated with ChAdOx1. No positive associations were seen between BNT162b2 and thrombocytopenic, thromboembolic and hemorrhagic events.
Additional Info
Disclosure statements are available on the authors' profiles:
First-Dose ChAdOx1 and BNT162b2 COVID-19 Vaccines and Thrombocytopenic, Thromboembolic and Hemorrhagic Events in Scotland
Nat. Med. 2021 Jun 09;[EPub Ahead of Print], CR Simpson, T Shi, E Vasileiou, SV Katikireddi, S Kerr, E Moore, C McCowan, U Agrawal, SA Shah, LD Ritchie, J Murray, J Pan, DT Bradley, SJ Stock, R Wood, A Chuter, J Beggs, HR Stagg, M Joy, RSM Tsang, S de Lusignan, R Hobbs, RA Lyons, F Torabi, S Bedston, M O'Leary, A Akbari, J McMenamin, C Robertson, A SheikhFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Hematological toxicities of COVID-19 vaccination were examined among 1,710,000 individuals after receiving their first dose of the ChAdOx1 vaccine and 820,000 after receiving their first dose of the BNT162b2 vaccine. These toxicities were identified using linked Scottish national health data.1 There were no excess toxicities among those receiving the mRNA BNT162b2 vaccine. The adenoviral vector ChAdOx1 vaccine was associated with: an increase in thrombocytopenia of 1.33 events per 100,000 vaccinations, most of which were ITP (an increase of 1.13 events per 100,000 vaccinations); an increase in venous thromboembolism events of 4.46 per 100,000 vaccinations; an increase in arterial thromboembolic events of 5.87 per 100,000 vaccinated for those aged 16 to 39 years and 31.35 per 100,000 vaccinated for those between 40 and 59 years; and an increase in bleeding events of 2.22 per 100,000 vaccinated for those aged 16 to 39 years and 2.18 per 100,000 vaccinated for those between 40 and 59 years. In comparison with non-vaccinated–matched controls, only ITP emerged as a likely association, whereas venous thromboembolism, arterial thromboembolism, and hemorrhage were only a suggestive association. The study was insufficiently powered to provide estimates of the rarer vaccine-induced thrombotic thrombocytopenia, cerebral venous thrombosis, and splanchnic vein thrombosis.2
These results provide a solid substrate of information to share with those considering vaccination. They also reassure the healthcare community about the relative safety of COVID-19 vaccination. Finally, results presented should provide excellent baseline data for monitoring hematological toxicities after a second vaccination dose, and, if needed, after booster doses are administered.
References