2024-05-04 10:34:49
Updated Saturday, May 4, 2024 – 12:34
The pharmaceutical company AstraZeneca has admitted for the first time, in official documents, that its vaccine against Covid-19 can cause rare adverse effects such as thrombosis, a complication that was already known and that already caused the limitation of the use of the product in 2021. .
This is the chronology of what happened.
What is the vaccine like?
The AstraZeneca vaccine, developed in collaboration with the University of Oxford, is based on the modification of an adenovirus so that it contains genetic information of the SARS-CoV-2 and is capable of awakening a reaction of the immune system to the pathogen.
When was it approved?
On January 29, 2021, the European Medicines Agency gave green light for AstraZeneca vaccine, in the middle of open war between the Swiss pharmaceutical company and the European Commission for the announced delays in the first shipments due to alleged production problems.
When were side effects detected?
During the clinical trials of the vaccine, in September 2020, the evaluation was momentarily suspended after the detection of a serious adverse event in one of the participants. However, after evaluating the problem, the trials continued.
After the product was approved by the European authorities, in March 2021 the administration of the vaccine was suspended for a few days after the notification of “several cases of thrombotic events in some European countries, including Espaatemporally related to the vaccination against Covid-19 AstraZeneca“.
Later, in April 2021, the European Medicines Agency (EMA for its acronym in English) recognized a “possible link” between the Covid-19 vaccine of AstraZeneca and very rare and unusual cases of thrombotic problems associated with a decrease in blood platelet levels.
The European body indicated that this complication should be included in the list of possible adverse effects of the product (specifically in the section of very rare effects). However, the EMA stressed that these were very rare complications and thathe benefits of the vaccine continued to outweigh its risks.
What happened to the vaccine?
In most countries its indication was limited to those over 60-65 years of age (in the United Kingdom this limitation was applied to those over 40 years of age). Regarding the second dose of the product, despite the fact that the European Medicines Agency (EMA), in light of scientific evidence, recommended complete the schedule with the second dose of AstraZenecaIn our country, the decision was made to vaccinate primarily with Pfizer, after an express study carried out by the Carlos III Health Institute confirmed the safety and effectiveness of the measure.
What are thrombotic events associated with the vaccine?
These are cases of cerebral venous thrombosis (specifically thrombosis of cerebral venous sinuses) with the particularity, details the AEMPS, that these thromboses are associated with a decrease in the number of platelets in the blood“which would suggest an abnormal activation of the coagulation system that would result in that obstruction of the cerebral veins“.
What are the mechanisms that explain this association?
At the time, the European Regulatory Agency suggested that a possible explanation for this observed association is a autoimmune reaction similar to that sometimes seen in patients treated with a common anticoagulant, the heparin.
In the body, heparin binds to a protein called platelet factor 4. However, in rare cases, after this union the immune system produces antibodies against the complex formed, which triggers an uncontrolled coagulation phenomenon and affects the available levels of platelets. This complication is called heparin-induced thrombocytopenia (HIT) and is similar to that observed in some of the patients studied following vaccination with AstraZeneca (which is why the syndrome has been called VIPIT, from English immune thrombocytopenia). vaccine-induced prothrombotic disease).
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