AstraZeneca and Jansenn are the two vaccines that are currently in the eye of the storm for a series (few) of dramatic reactions that have affected vaccinated people. The problem relates to the development of blood clots in the brain which seem to affect women under 60 years of age much more.
At the moment no one knows exactly how this happens but several factors could explain part of the phenomenon.
The six patients who had blood clots after receiving the Janssen vaccine in the United States are women. After these cases, the FDA (the Food and Drug Administracion) asked to stop the vaccination. And the company that makes the vaccine – Johnson & Johnson – has suspended distribution in Europe.
With the AstraZeneca vaccine, the European Medicines Agency has detected 222 cases of thrombi out of 35 million vaccinated, one case every 175,000 immunized, a very low incidence.
Again, the majority of those affected are relatively young women.
Now two German and Austrian medical teams have explained how blood clots occur in people vaccinated with the AstraZeneca vaccine.
The results indicate that the immune system turns against the patient itself and generates antibodies that bind to a protein on the surface of the platelets. These blood cells are responsible for blood clotting. When antibodies bind to that protein, platelet factor 4, the platelets become activated and begin binding together, producing thrombi.
The nine patients studied in Germany and Austria were women. Most had clots in the blood vessels of the brain or abdomen. In both Germany and Austria, the first two cases occurred in two health workers aged 49 and 37.
What has been seen after vaccination is very similar to a very rare reaction already seen among patients treated with heparin, an anticoagulant.
German and Austrian health professionals speculate that the reactions may be due to the type of vehicle used by the AstraZeneca and Janssen vaccines: two types of adenoviruses. The former uses an inactivated chimpanzee adenovirus and the latter a disabled human adenovirus.
There are two other vaccines that also use adenovirus, Sputnik V and Chinese Cansino. There are no known reactions to these two vaccines, but the two countries that produce them have never been examples of great transparency.
Why do thrombosis affect women the most?
First, women suffer from more autoimmune diseases than men and the younger they are, the more active their immune systems are and the more susceptible to a complication like this. Another risk factor is the contraceptive pill which slightly increases the risk of blood clots.
The risk associated with the pill is far greater than that of vaccination.
On this issue, EMA data indicate that one in 1,000 women who take the contraceptive suffers from a clot, while the risk among those vaccinated is one in 175,000.
Under normal conditions, cerebral sinus thrombosis, the most common reaction seen in people vaccinated with AstraZeneca and Janssen, is much more common in women in their thirties.
Of course the communication was very confused at all levels but in any case all the experts agree that the very rare appearance of these thrombi must not affect the vaccination process. The risks of these complications are far less than the benefits of getting vaccinated.