Post-vaccination thrombocytopenic immune syndrome. Causation or casuality? Special reference to Astra-Zeneca COVID-19 (Vaxzevria®) and Johnson & Johnson vaccines

As vaccination against COVID-19 advances in the world, approximately to date, more than four thousand million of vaccines doses have been administered, adverse reactions to its administration are also reported, especially with the placement of the first dose. The alarms have been triggered by the report of a series of cases with manifestations of thrombosis and thrombocytopenia after vaccination with Vaxzevria® (AstraZeneca Laboratories) and Johnson & Johnson vaccine, the WHO, the European Medicines Agency (EMA), and the CDC through pharmacovigilance committees analyzed the cases and issued provisional statements mentioning that, although a cause-andeffect relationship of the vaccination seems plausible, it is not confirmed. In the present review, possible pathological scenarios that could explain these cases are analyzed, to which the term Vaccination-induced Thrombotic Immune Thrombocytopenia (VITT) has been placed. However, we believe that it is very premature to establish a firm causality taking into account the incidence of thrombosis in the general population and the very low proportion of cases in relation to the total of vaccinated worldwide, it can also be assumed that the reported number of thromboembolic episodes among receptors who have received the COVID-19 Oxford-AstraZeneca and Johnson & Johnson vaccines do not appear to increase in relationship to the expected number estimated from the incidence rates of the entire population before the introduction of the vaccination program. It is concluded that it is necessary to rule out a causal link between these events and the vaccine, so far, the obvious benefits of the vaccine far outweigh the risks of post-vaccination. © 2021 Academia Nacional de Medicina. All rights reserved.