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Covid-19: Pharmacovigilance: Thrombus Trackers and Other Adverse Effects of Vaccines | Society


The most serious side effects of covid vaccines have been a tragedy for the few who have suffered them, a setback for the immunization plan and a success for the pharmacovigilance system. In other circumstances, such sporadic cases could have gone unnoticed for years by the health authorities, but a massive vaccination in a very short time, combined with a detailed and meticulous follow-up, have allowed them to be detected, associated with the drug that produces them and to take measures in question. weeks.

At the moment, the only serious and unexpected side effect associated with vaccines has been venous thrombi combined with a drop in platelets that occur as a very rare immune response after the injection of AstraZeneca (one for every 200,000 punctures in Spain) and, to a much lesser extent, from Janssen (less than one per million in the United States).

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To locate them, there is a well-oiled mechanism that passes through the vaccination point, the primary and specialist clinics, as well as the emergency units, which notify them to a centralized system of the Spanish Agency for Medicines and Health Products (AEMPS). The process ends when, if necessary, it is analyzed by a team of experts who confirm or rule out that the case is due to vaccines.

It all starts before the vaccinations themselves begin. The Spanish health authorities and the rest of the countries, together with the European Medicines Agency (EMA), review the frequency with which certain pathologies occur in the population that, although they have not been detected in clinical trials, are candidates for appear after punctures when applied to millions of people. Thrombi were one of them. Knowing the probability that they appear in a normal situation is crucial: when practically the entire population is going to receive a drug, it is inevitable that these events will continue to occur. The key is to see if you increase your frequency with vaccinations. There the alarms go off.

And this happened in Europe on the weekend of March 13. Although there were some warnings days before, the clots were not really an anomaly with respect to the forecast. But the appearance in several countries, Spain among them, of these strange thrombi with thrombocytopenia, began to make regulators think that vaccines could be causing them. They were still few and it was difficult to establish without a doubt causality. The EMA went to work and found it three weeks later: the AstraZeneca vaccine played a role in this side effect.

Until then, at the point of vaccination, citizens were recommended (or so it should be) that in the event of any unexpected effects, they should inform their doctor or the health authorities of those that went beyond mild headaches. , fever, malaise and pain at the point of the puncture, among others. There is a web (notified) in which both individuals and professionals can report these events, which are recorded by the AEMPS so that it can investigate when a serious event has an abnormal frequency.

Identify symptoms

But once it was known that there was already a serious side effect identified, the magnifying glass was put on it. This type of thrombi has very particular characteristics that both the vaccinated population and the doctors have to be aware of: it can have a sudden onset, it can be located only on one side of the head, it worsens when the patient is lying down or exercising, It interrupts the night’s rest and, in addition to not responding to the usual treatments for the headache, it progressively worsens. This happens in the brain, but it can also occur in the belly, lungs, or legs. Vomiting, abdominal swelling, shortness of breath, coughing up blood, tingling, flushing, are some characteristic symptoms in these other parts of the body, where thrombi have been less frequent. Both the Ministry of Health and the autonomous communities have websites with information on these signs. Especially detailed is, for example, that of Andalusia.

The first thing, when a doctor is presented with an abnormal condition, before even notifying it, is to treat it. Lorenzo Armenteros, spokesman for the Spanish Society of General and Family Physicians (SEMG), explains that both the communities and the Anglo-Swedish pharmacist itself, through medical societies, have made an effort to inform physicians of the symptoms of these thrombi so that they do not go unnoticed and are dealt with appropriately quickly.

Queue of people waiting to be vaccinated in the Olympic State of Seville on May 20.
Queue of people waiting to be vaccinated in the Olympic State of Seville on May 20. PACO PUENTES / EL PAÍS

Patients basically have two ways to be cared for when they present these symptoms: the primary or emergency physician. In these units there are established protocols so that the treatment is adequate. Juan González del Castillo, spokesman for the Spanish Society of Emergency and Emergency Medicine (Semes), explains that the first thing to do when the aforementioned symptoms are detected is to ask if the vaccine has been received between 3 and 21 days before. If so, it is analyzed if there is a drop in platelets. So, the treatment for the thrombus is not the one that would be applied normally, since this symptom, very abnormal, makes frequent anticoagulants counterproductive.

“After doing a series of tests, we use anticoagulants other than heparin in suspected cases. We also avoid transfusing platelets, ”says Del Castillo. By properly identifying the disease, the chances of successful treatment are very high.

After the clinical approach, a blood test is done to look for platelet antibodies. This is a sign that an immune reaction has occurred that has affected the platelets. All this is analyzed by a team of experts that advises the AEMPS and determines whether the cases are related to the vaccine or not.

This team is made up of half a dozen specialists –hematologists, neurologists and clinical pharmacology specialists– appointed by the Federation of Spanish Scientific Medical Associations (Facme). The head of the vaccination group of this institution, Cristina Avendaño, explains that the collaboration with the AEMPS is constant, but that as soon as they suspected of this type of side effects they resorted to them. “It is very important to find the right experts for each case, and that is what we do, together with medical societies. It is not about having a team of specialists for anything, but selecting the best. We do it to analyze the effects of other drugs, but in the case of vaccines we are giving a response in real time ”, he emphasizes.

This team analyzes each case: all their clinical history, analysis, tests, in contact with the specialists who have treated them. AEMPS sources point out that the main markers to determine the relationship of thrombi with the vaccine is the lowering of platelets and the presence of this specific type of antibodies, which are the ones that give the definitive clue that the vaccine has triggered this response immune. With this methodology, according to the latest data provided by the agency, 20 cases and four deaths had been identified in Spain. One more was under study. All caused by AstraZeneca.

Four cases of strange thrombi also came to the team after receiving Pfizer, but they did not meet all the necessary characteristics to relate them to the drug, so they determined that they occurred later, but they were not linked. There was correlation, but no causality. And this is the key. Because vaccines are not going to prevent blood clots, heart attacks, cancers or car accidents from occurring. The key to pharmacovigilance is to detect if they are associated with them.


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