New blow to vaccination campaigns against COVID-19: after the appearance of several cases of thrombi in the United States in people who had received the Janssen vaccine, the health authorities of this country have announced that they will pause immunization with this drug until its relationship to these blood clot episodes is investigated. After this announcement, the pharmaceutical company Janssen announced its decision to delay the delivery to Europe of its single-dose vaccine against the coronavirus, so the first 300,000 doses that were to land in Spain this week will still be late in arriving.
While this very rare potential side effect, which has also been detected in the Astrazeneca vaccine, needs to be thoroughly analyzed, many experts insist that the risk of further slowing vaccination campaigns against COVID-19 is even greater. “While a causal link between certain COVID-19 vaccines, platelet abnormalities and blood clots has not been confirmed so far, the index of suspicion that these rare cases may be caused by the adenovirus component of the AstraZeneca and J&J vaccines is increasing. ”Explains to the Science Media Center the professor of immunology and infectious diseases of the University of Edinburgh Eleanor Riley. “More data needs to be collected and the implications carefully considered, but the truth is that for the vast majority of adults in Europe and the US the risks associated with contracting COVID-19 far outweigh any risk of being vaccinated. In addition, increasing awareness about the possibility of such side effects means that they can be diagnosed more quickly and treated more effectively, “he concludes.
Ian Douglas, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, agrees that these six cases of thrombi with Janssen’s vaccine are very similar to those seen with Astrazeneca, although it is vital to insist on the benefits associated with achieving immunity against SARS-CoV-2 with the vaccine : “All indications are that this is an incredibly rare effect, in this case and based on the data available so far, around a one in a million chance for Janssen’s vaccine To put this in perspective, it is about the same chance of being struck by lightning in any given year in the UK. On the other hand, the risks of COVID-19 are substantial. If the 6.8 million people who received the Janssen vaccine in the US were infected with the virus, it is likely that several thousand died and many more, including younger adults, would experience severe and long-lasting sequelae, “he explains to Science Med. ia Center .
Thrombi, an adverse effect of many drugs
As the professor of the area of Cell Biology at the Pablo de Olavida University (Seville), Guillermo López Duch, recalls in an article published today in The Conversation, “thrombocytopenia or thrombosis with reduced platelets is a symptom that also appears in response to drugs. Antibiotics such as vancomycin, antidepressants such as mirtazapine, antiallergics such as Rizaben, sulfonamides against infections such as cotrimoxazole or, curiously, treatment with anticoagulants such as heparin can cause thrombocytopenia. In fact, the cases of thrombocytopenia associated with the Astrazeneca and Jannsen vaccines have shown similarities with that generated by the heparin treatments ”.
In any case, experts agree on the importance of these facts being thoroughly analyzed and investigated as soon as possible: “Although it is too early to draw conclusions, the development of the facts raises the possibility that at least some adenovirus vectors, already either by themselves or in combination with the gene of protein S of the SARS-CoV-2, can cause this idiosyncratic reaction in a very small proportion of individuals “explains Science Media Center professor of Pediatrics, University of Bristol Adam Finn. “This can give us clues to understand the mechanism or find a way to prevent this problem from occurring. Given the importance of these vaccines for the timely control of the pandemic, the investigation of this phenomenon is now an international priority of extreme urgency ”, he concludes.
