According to a study, still in progress, vaccines using the a viral vector type AstraZeneca e Johnson & Johnson they could be associated with the rare thrombosis events recorded around the world.
In viral vector vaccines, the pharmacologist explains to ANSA Antonio Clavenna of the Public Health Department of the Mario Negri Institute in Milan, "Viruses modified in the laboratory are used because they are unable to replicate once introduced into the organism. In the case of AZ and J&J, adenoviruses are used, generally responsible for infectious processes affecting the upper respiratory tract". For Az it is a chimpanzee adenovirus and for J&J it is a human adenovirus. Clavenna explains that "these inactivated viruses are used as transporters to introduce the DNA of the new coronavirus SarsCov2 into the human body with the instructions to manufacture the Spike protein, which is distinctive of the new coronavirus itself. Once the vector with the instructions is introduced, some cells of our immune system begin to produce Spike and the immune system is activated against the protein, which it recognizes as something 'different' and dangerous, and produces antibodies which, if the subject enters in contact with the real virus, they will protect it from infection ".
So explains the pharmacologist, "The viral vector vaccines authorized by the European Medicines Agency Ema and the Italian Medicines Agency Aifa work, namely the Vaxzevria vaccine by AstraZeneca in two doses and the COVID-19 Vaccine Janssen by J&J which is instead single dose".
Both vaccines are now under the attention of health authorities after the very rare cases of thrombotic events that have been reported following vaccinations, and which today led the US authorities to suspend immunizations with the J&J product. The hypothesis under study, continues Clavenna, it is that the viral vector may be somehow connected to the mechanism that triggers these rare adverse events.
That is, the pharmacologist of the Mario Negri Institute in Milan explains better, "the organism, in particular cases and for currently unknown reasons, would still recognize the vector as a foreign element, producing antibodies against it. These antibodies, in addition to recognizing the viral vector, would also recognize and bind to some substances normally produced by the organism itself and which are part of the coagulation process. Thus, these antibodies would have the effect of triggering the coagulation process even if not necessary, leading to the rare thrombotic events ".
However, Clavenna is keen to point out that "however this is only a hypothesis, there are still several doubts to be clarified and further studies are needed". However, the pharmacologist concludes, "if this study is confirmed, there are therapeutic solutions capable of acting and preventing these phenomena of hypercoagulation ".