Seven residents of the United Kingdom who were vaccinated against coronavirus with the Oxford University-AstraZeneca vaccine have died from thrombosis in atypical circumstances. The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has confirmed this information, according to the BBC. However, there is no accurate data yet on whether these diagnoses were directly related to the vaccination or if they were coincidental.
In total, 30 out of 18 million people in the UK who received the AstraZeneca vaccine on March 24 experienced a blood clot. The British regulator insists that the benefits of vaccination outweigh any risks. The World Health Organization and the European Medicines Agency have come to the same conclusion. “The safety of patients remains our top priority,” said an official representative of the company AstraZeneca. However, due to concerns about the safety of the vaccine, authorities in some other countries, including Germany, France, the Netherlands and Canada, have decided to administer this drug only to the elderly.
On Friday, the MHRA published data showing that 22 cases of sinus thrombosis of the cerebral cortex (STCC) – a rare diagnosis in which blood clots form in the brain – were detected among those vaccinated. In addition, these individuals had low levels of platelets in their blood, which are one of the factors that contribute to the development of thrombosis. The UK regulator also identified eight other cases where patients had other thrombosis-related problems but their platelet counts remained low. The MHRA confirmed in an email to the BBC that “seven people [out of 30] have sadly died”.
“The benefits of preventing Covid-19 infection and its consequences continue to outweigh any risks and residents should continue to be vaccinated when invited,” said June Raine, Chief Executive of the MHRA.
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Meanwhile, experts continue to investigate whether AstraZeneca’s vaccine can cause such rare cases of thrombosis. This week, the European Medicines Agency said it was “unproven but possible”. There are two circumstances that raise suspicion. First, these are unusual thrombi: they occur with low levels of platelets and specific antibodies associated with certain types of thrombosis. “This increases the likelihood that this vaccine may be a causal factor in these rare and unusual cases of cerebral venous sinus thrombosis (CVST). Although we do not currently know this for certain, urgent research is needed,” said Professor David Werring of the Institute of Neurology at University College London, according to the BBC. The second suspicious circumstance is the difference between the vaccines produced by AstraZeneca and Pfizer/BioNTech. In the case of the latter, two cases of TTS have been reported in the UK out of more than 10 million vaccinated individuals – and these patients did not have low platelet levels. However, experts are still unsure how common this type of thrombosis is. Estimates range from two cases per million people per year to nearly 16 cases per million – and that is in the pre-Covid 19 era. In addition, the coronavirus itself is associated with an increased risk of thrombosis and may also cause an increase in the number of cases of TTS. In Germany, there are 31 known cases of TTSOM and nine deaths out of 2.7 million people who received the vaccine, with the majority of diagnoses in middle-aged and young women. Data on the specific population groups affected by thrombosis in the United Kingdom have not been published, but it is believed that a wider range of patients have been affected.
Serious side effects can occur with all medicines, from vaccines to acetaminophen. Regular flu shots are known to cause Guillain-Barré syndrome, a nerve disorder, in one case in a million. So in this case, the main question is, is the risk justified? Even if we assume that vaccines were indeed the cause of the disease, which has not yet been proven, the statistics indicate a likelihood of one death per 2.5 million vaccinated individuals. Let’s compare these data with the proven threat of coronavirus. If 2.5 million 60-year-olds are infected with Covid-19, about 50,000 of them will die. If the same number of 40-year-olds are infected, about 2,500 will die. Experts will continue to evaluate this risk-benefit balance as new data become available and as the vaccination program expands to younger individuals who are less susceptible to the risk of death from Covid-19.
As Professor Paul Hunter, a microbiologist at the University of East Anglia, told the BBC, there is growing evidence that thrombosis may indeed be linked to AstraZeneca’s vaccine, but the benefits of vaccination still far outweigh the risks. “The cases in which clusters of rare diseases occur completely by chance are well known. But when such a cluster is identified in one country and then appears in another country – as in the case of Germany and now England – it seems to me that the likelihood of a random coincidence is very low,” says Hunter. “It is clear that more research needs to be done, but it seems to me that the evidence is beginning to point to a cause-and-effect relationship,” he says. However, health expert Professor Linda Bauld of the University of Edinburgh noted on the BBC that cases of thrombosis are “rare” and “at the moment there is no basis to say that there is a cause-and-effect relationship, that the vaccine leads to such outcomes”. She urged the country’s residents to get vaccinated, adding, “Covidien itself significantly increases the risk of thrombosis, and it is not excluded that this may be related to the reasons we are seeing”.