Spotlight on Adenovirus-Based Vaccines and Rare Thrombotic Events

摘要

A recent paper from Moonla et al addressed the huge concern of coagulation disorders in COVID-19.1 The current debate about blood clots, following administration of some vaccine formulas, is harassing the scientific community. Experts in the field are striving to make people trusted about the negligible hazard associated with those vaccines. Yet, truth is hidden within some fundamental evidence, which deserves further research. A paper from Stone et al, published on 2007, showed that the delivery of the recombinant adenovirus-based vectors (serotype 5) used for therapy, caused platelet sequestering, thus triggering their activation and also aggregation, which were followed by their entrapment in the liver and finally their capture by Kupffer cells.2 Adenovirus serotype 5 (Ad5) is widely used as a recombinant, non replicative vector even for COVID-19 vaccine formulations3,4 and the ability of Ad5 vectors to sequestering platelets, causing temporary thrombocytopenia, has been widely demonstrated.5,6 Moreover, it seems that Ad5 binds the platelets CD62 and increases D-dimer for at least 6 hours following Ad5 introduction.2 Recombinant Ad5 therefore can activate platelets. Despite this in vitro evidence may suggest some criticism about Ad5-based therapy and support caution in addressing Ad5 vaccine based safety, the rate of thrombogenic adverse effects is negligible, amounting to less than 0.00034%.7,8