Why post-vaccine thrombosis affects women more

The six cases of thrombosis – one of them fatal– reported in the United States in people who received the Johnson & Johnson vaccine and which led to the suspension of vaccination with this formulation in this country occurred in women.

With the AstraZeneca vaccine, until March 4, the European Medicines Agency (EMA) had detected 222 cases of thrombus among 35 million vaccinated, which would be equivalent to one case per 175,000 vaccinated. Again, the majority of those affected were relatively young women.

In Spain, 12 cases are under investigation among more than 2.5 million people vaccinated with AstraZeneca, according to data last Friday. To these must be added that of a man from Castilla-La Mancha whose death after being vaccinated is under study, according to the newspaper. The country.

While waiting for the Food and Drug Administration (FDA) to analyze the cases in the United States, the pharmaceutical company Johnson & Johnson suspended the distribution of its vaccine in Europe. Regarding the formulation of AstraZeneca, on the other hand, the European regulatory agency has decided not to vaccinate women under 30 in the Old Continent.

Consulted by Infobae, the hematologist member of the Argentine Society of Hematology José Ceresetto (MN 74596) explained that “the mechanism by which this occurs was very well described by the German Andreas Greinacher at the time of what happened in first place with the AstraZeneca vaccine and I named it vaccine-induced immune thrombocytopenia; It is not that the clot occurs spontaneously, but that the virus inoculated in the vaccine modified so that it is harmless to humans and generates defenses against COVID-19 generates this effect in the immune system“.

For him, “This is a rare combination that occurs immediately after the vaccine against low platelet count and generation of thrombi and something which has already been observed induced by heparin is an immune response which occurs due to the presence of antibodies against a coagulation factor (platelet factor 4) which is activated and causes platelet thrombi to form ” .

The hematologist at the British Hospital considered it a “new rare disease” and pointed out that it “has been observed in young women”. According to him, it is because “In general, young women are predisposed to have autoimmune diseases.”

Neurologist Conrado Estol (MN 65.005) agreed with him, who pointed out that the explanation of why this phenomenon occurs more in women is “because it is an autoimmune problem, it is that is, the person makes antibodies against themselves and women have a different immune system because immunity is largely given by the X chromosome and women have two“. “On the one hand, they have had less COVID infection and fewer severe cases, but in immune reactions they can be worse,” he said.

So, apparently, while it’s not yet clear why thrombi affect young women more, specialists agree that there are factors that may help explain it. In the first place, “women suffer more from autoimmune diseases than men and the younger they are, the more active their immune system is and they may be more susceptible to a complication like this, ”said Rodrigo Rial, spokesperson for the Spanish Society of Vascular Surgery, which added another risk factor that only affects some young women: “The contraceptive pill slightly increases the risk of thrombi. The risk associated with the pill is much greater than that of vaccination ”.

About one in 1,000 women who take the contraceptive will suffer from such a clot, while the risk among those vaccinated is one in 175,000, according to the latest data from the European Medicines Agency.

Added to the question of why women are the target of this adverse reaction from vaccines to prevent COVID-19, which is why – so far – it has only been reported in these two formulations.

It is speculated that this may be due to the type of vehicle or vector used by the AstraZeneca and Johnson & Johnson vaccines: two types of adenovirus. The first uses an inactivated chimpanzee adenovirus and the second uses a disabled human adenovirus.

There are at least two other approved vaccines that also use adenovirus, Russian Sputnik and Chinese Cansino.

For Flock, “The structure of the vaccine is similar in both but there is no clear explanation why this vaccination platform could generate such an immune response.”

Greinacher agrees with the need for more data. But it says that alerting doctors to the possible complication is crucial. When detected early, heparin-induced thrombocytopenia can be treated with immunoglobulins (non-specific antibodies from blood donors) that help slow platelet activation. For him, the induced vaccine “must be treated in the same way”.

After stressing that “in the United States, this vaccine was applied to rural populations, who are difficult to access because they thought they would have the greatest difficulty in applying a second dose,” Estol pointed out: “If detected early, this thrombosis is not treated with anticoagulants because it is caused by an immunological phenomenon, so immunological treatment is given instead.”

One of the problems is that there is no known marker that can tell who will experience this very rare side effect. What exists is a possible treatment already used in patients who react badly to heparin: stop administering this anticoagulant and give gamma globulin, a type of blood protein.

“It doesn’t happen immediately after vaccination as it does with allergic reactions, but rather within two weeks,” said Estol, for whom “the benefit of being vaccinated outweighs the risk of infection”.

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