Hypotheses behind the very rare cases of thrombosis with thrombocytopenia syndrome after SARS-CoV-2 vaccination. Issue 203 (July 2021)

• Record Type: Journal Article
• Authors: Douxfils, Jonathan; Favresse, Julien; Dogné, Jean-Michel; Lecompte, Thomas; Susen, Sophie; Cordonnier, Charlotte; Lebreton, Aurélien; Gosselin, Robert; Sié, Pierre; Pernod, Gilles; Gruel, Yves; Nguyen, Philippe; Vayne, Caroline; Mullier, François
• Is Part Of: Thrombosis research. Issue 203(2021)
• Page Start: 163
• Page End: 171
• Publication Date: 2021-07
• Subjects: COVID-19 -- Vaccines -- Thrombosis -- Cerebral venous sinus thrombosis -- AZD1222 -- ChAdOx1 nCov-19 -- COVID-19 Janssen vaccine -- Ad.26.COV2.S; Thrombosis -- Periodicals; 616.135
• DOI: 10.1016/j.thromres.2021.05.010
• Languages: English
• ISSNs: 0049-3848

Abstract

Abstract: As of 4 April 2021, a total of 169 cases of cerebral venous sinus thrombosis (CVST) and 53 cases of splanchnic vein thrombosis were reported to EudraVigilance among around 34 million people vaccinated in the European Economic Area and United Kingdom with COVID-19 Vaccine AstraZeneca, a chimpanzee adenoviral vector (ChAdOx1) encoding the spike protein antigen of the SARS-CoV-2 virus. The first report of the European Medicines Agency gathering data on 20 million people vaccinated with Vaxzevria® in the UK and the EEA concluded that the number of post-vaccination cases with thromboembolic events as a whole reported to EudraVigilance in relation to the number of people vaccinated was lower than the estimated rate of such events in the general population. However, the EMA's Pharmacovigilance Risk Assessment Committee concluded that unusual thromboses with low blood platelets should be listed as very rare side effects of Vaxzevria®, pointing to a possible link. The same issue was identified with the COVID-19 Vaccine Janssen (Ad26.COV2.S). Currently, there is still a sharp contrast between the clinical or experimental data reported in the literature on COVID-19 and the scarcity of data on the unusual thrombotic events observed after the vaccination with these vaccines. Different hypotheses might support these observations and should trigger further in vitro and ex vivo investigations. Specialized studies were needed to fully understand the potential relationship between vaccination and possible risk factors in order to implement risk minimization strategies. Highlights: Vaxzevria® and COVID-19 Vaccine Janssen have been associated with rare case of thrombotic with thrombocytopenia syndrome. Main mechanism explaining the risk involved antibodies directed against platelet factor 4. Research of other physiopathological mechanisms has not been sufficiently investigated and should not be discarded. There is a contrast between the clinical or experimental data on COVID-19 and the scarcity of data with these vaccines. The benefits of these vaccines are well established and the risk-benefit balance remains largely positive.