Society 08/04/2021

"The risk of thrombosis is more frequent with contraceptives than with the vaccine".

We clarify some of the doubts generated as a result of the changes in the vaccination with AstraZeneca

1 min
One vial of the Oxford and AstraZeneca vaccine

BarcelonaThe European Medicines Agency (EMA) has concluded that thrombi may be a side effect of the AstraZeneca vaccine in very rare cases and recommends continuing with the vaccination, as it argues that the benefits outweigh the risks. However, some countries have changed their vaccination schedule, including Spain, which will now vaccinate only the over-60s with AstraZeneca. This rare clotting disorder occurs in one case per 300,000 inhabitants "and in Europe there are 25 million people who have received the vaccine," says Carlos Molina, head of the stroke unit of the Hospital de la Vall d'Hebron, who believes that this does not justify stopping the vaccination campaign. "I think it is a decision that does not conform to scientific arguments that support the non-vaccination of a certain population group. A few weeks ago it was not possible to vaccinate those over 55 years and now only those over 60 years, there is no robust scientific justification. The benefit of the vaccine is far above the potential risk," says this doctor. We have spoken with him to clarify the doubts and fears that the AstraZeneca vaccine has generated.

What is the risk of suffering thrombosis as a result of the vaccine?

Cases of thrombosis reported after vaccination with AstraZeneca are one in 300,000. "The risk of cerebral venous thrombosis is more frequent with contraceptives, which is 2%, and nobody stops taking contraceptives," says the head of the stroke unit at Vall d'Hebron Hospital, who also explains that behind women who have suffered thrombosis after taking contraceptives there is "an underlying coagulation problem".


The thromboses reported by AstraZeneca's vaccine - which they have named "vaccine-induced prothrombotic immune thrombocytopenia (VIPIT)" - resemble heparin-induced thrombosis, although it is, as with the vaccine, "a rare complication". "It is stated in the drug's data sheet, but it is not a reason not to use the drug or the vaccine," says Molina. "It is much more frequent with heparin - approximately every 80,000 cases - than with the vaccine, but it has been detected in clinical trials and is treated. The drug is not withdrawn because the benefits far outweigh the problem," he adds. He adds that the risk of thrombosis if you get covid is higher. "The combination of stroke and covid is one of the worst there is," he says. "These complications happen, and if you look at any drug's package leaflet you get scared, but it should be stated and documented for the information of patients," adds Molina, who insists that the benefit of the vaccine against the coronavirus is "much higher than the small percentage that may suffer thrombotic processes". "People are concerned about the contradictory information, and rightly so, but the message should be one of reassurance because this is part of normal clinical practice: all drugs and vaccines have side effects, they are evaluated and we move on," he explains.

What is that thrombosis?

Cerebral venous thrombosis is a very rare form of stroke, with three to four cases per year. VIPIT is an immunological reaction due to a side effect of a drug or vaccine. When the vaccine is administered, an autoimmune response is generated to protect against covid, but there are rare cases where a cross-response can also occur and antibodies are generated, which also act against the structure of platelets. "The platelets clump together and decrease in number, and thrombotic phenomena occur in unusual locations". These thrombi are located in abdominal and cerebral veins, which are rare locations.

Can VIPIT be treated?

If detected early, vaccine-induced autoimmune thrombocytopenia can be treated with immunoglobulins and thus stop the thrombotic process.

What should I be looking out for?

It is normal to have a mild headache 24 to 48 hours after vaccination, which will go away with painkillers. However, if the headache is very intense, does not let you sleep, does not go away with painkillers, is accompanied by vomiting and blurred vision, is worse lying in bed, is more intense in the morning than in the afternoon and is accompanied by other neurological signs, such as loss of vision, loss of strength in the arm or leg and epileptic seizures, then you should consult a doctor and have an assessment. These symptoms appear in the first two weeks after vaccination.

Does it affect young women more?

The head of the stroke unit at Vall d'Hebron says that "it is not exclusive" to women. "But women have a higher percentage of autoimmune responses, and the vaccine generates a response of antibodies that go against the structure of platelets, which is more frequent in autoimmune diseases, which are more frequent in women than in men. However, there is also a selection bias, Molina points out, as in recent months older people have mostly received the Pfizer vaccine and younger people the AstraZeneca vaccine.

Are people suffering from autoimmune diseases or at risk of thrombosis more likely to suffer this side-effect?

Vaccination of people with autoimmune diseases, such as lupus or multiple sclerosis, is not contraindicated and they should not be at increased risk of induced thrombosis, Molina says. Nor should people with blood coagulation disorders be at increased risk of vaccine-induced thrombotic thrombocytopenia (VIPIT), "just as they are not at increased risk of heparin-induced thrombocytopenia".

What about if you have already had thrombosis caused by something else?

Only people who have already suffered from heparin-induced thrombosis should proceed "with caution", as the triggering mechanism is very similar to that of vaccine-induced thrombosis, explains Carlos Molina. "It is the only case to be taken into account, but it is very carefully considered, as they are extraordinarily rare cases."

Can people who have received the first dose of AstraZeneca get the second?

Molina says there is not enough data on cases of thrombosis with the second dose and he is in favour of administering it. "People who have already received the first dose should rest assured," he says.

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