Top US health authorities said on Friday that they have not yet found a "causal" link between Johnson & Johnson's Covid-19 shot and blood clots, as the EU drug regulator probed possible instances among those who have received the vaccine.
"At this time, we have not found a causal relationship with vaccination and we are continuing our investigation and assessment of these cases," said a statement from the US Food and Drug Administration.
The regulatory agency said it was aware of "a few individuals" in the United States who had suffered clots and low levels of platelets in the blood after receiving Johnson & Johnson's vaccine.
"Both conditions can have many different causes," the FDA said. "We will keep the public updated as we learn more."
EU vaccine safety probe
As US regulators continue monitoring the safety of the Johnson & Johnson shot, the EU has been more cautious, potentially adding more delays to vaccine rollouts across the continent.
Four cases, one fatal, of rare clots with low blood platelets were reported among those vaccinated with the shot, the European Medicines Agency (EMA) said in a statement.
The numbers of clot cases in people who took the shot have been small so far compared to the total number of people getting the vaccine worldwide, Peter Arlett, EMA’s head of analytics, said on April 7.
At that point, Mr Arlett said three clotting cases had been found, while some 4.5 million people had gotten the shot.
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Medical Staff prepare vials of the Pfizer/BioNTech vaccine at a vaccination center at the Messe trade fair grounds in Erfurt, Germany. Getty Images -
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A woman waits her turn for vaccination in the the vaccination center at the Messe trade fair grounds in Erfurt, Germany. Getty Images -
People, most of them elderly, wait in line to enter the Arena vaccination center in Berlin, Germany. Getty Images -
Medical staff in protective suits treat a patient suffering from the coronavirus disease in the Intensive Care Unit at Havelhoehe community hospital in Berlin, Germany. Reuters -
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Syringes are prepared to administer the AstraZeneca vaccine at a new mass vaccination centre in WiZink sports arena in Madrid, Spain. Reuters -
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People wait to receive a dose of a vaccine in Nogent-sur-Marne, near Paris, France. EPA
“I think it would be fair to say there is intensive monitoring of this issue across the vaccines,” Mr Arlett said.
The report from the EMA is the first to mention a probe of blood clots associated with the Johnson & Johnson vaccine.
The FDA said it was aware of the EMA's statement and provided the agency with the data that formed the basis of its report.
The EMA's statement follows an investigation of blood clots in the brain reported by some people given the AstraZeneca vaccine, which has prompted some European countries to change their vaccine recommendations.
In its report on Friday, EMA's safety committee said unusual blood clots linked with low blood platelets should be listed as very rare side effects of the AstraZeneca vaccine.
It has also started to investigate reports of capillary leak syndrome – which causes blood vessel swelling and a drop in blood pressure – in five people who received the AstraZeneca vaccine. The safety panel said it was not clear whether these were linked with the vaccine. AstraZeneca did not immediately respond to a request for comment.
Ian Douglas, a professor of pharmacoepidemiology at London School of Hygiene & Tropical Medicine, said the reports were part of a normal process in which the EMA's safety committee reviews important safety signals as they arise.
