A new hypothesis proposes the cause of extremely rare blood clots and platelet depletion associated with the use of Oxford AstraZeneca or Johnson & Johnson/Jansen COVID-19 vaccines. Several studies have suggested physiological mechanisms to explain such reactions, but the underlying root cause and rarity of these events have not yet been explained.
A paper published in the journal Medical Hypotheses[1] now proposes that the reaction is due to inadequate protection of the adenovirus vaccine vector. Normally, each virus particle can be protected by a coating of the naturally-occurring coagulation factor X protein. The new hypothesis suggests that the factor X in affected individuals is unable to bind to the virus surface, leaving it exposed to other proteins such as platelet factor 4 and immunoglobulins. These can then form a compound structure with the adenovirus which the body identifies as foreign, eliciting an immune response, thrombosis and platelet depletion.
Testing a hypothesis relating to such rare events is challenging, because the experimental samples are scarce. This paper identifies an experimental route to prove or disprove the hypothesis, which acknowledges in the best scientific tradition that either outcome will be informative. Intriguingly, if proven correct, it also offers a solution which could potentially avoid this adverse side effect, enhancing confidence in the use of these vaccines to deliver global immunisation against COVID-19.
Queen’s House Consulting is pleased to have provided non-financial support for the research which generated this hypothesis in April 2021 and also for the subsequent efforts to publish the idea, so that other appropriately-resourced research groups can test the concept experimentally.
[1]Feldman PA. Proposed mechanism for rare thrombotic events after use of some Covid-19 vaccines. Med Hypotheses 159 (2022). doi: 10.1016/j.mehy.2021.110756