There is a causal link between AstraZeneca's COVID-19 vaccine and rare blood clots, a top official at the European Medicines Agency (EMA) said in an interview published Tuesday.
"It is becoming more and more difficult to affirm that there isn't a cause-and-effect relationship between AstraZeneca vaccines and the very rare cases of blood clots associated with a low level of [blood] platelets," Marco Cavaleri, head of health threats and vaccine strategy, told Rome's Il Messaggero newspaper. He added that he still endorses the shot and an EMA statement on the vaccine was coming this week.
Cavaleri added that while the EMA is anticipating to establish a link to the clots, the scientific reason for the clots is not known.
"In the coming hours, we will say that the link is there," he said. "How this happens, we still haven't figured out."
The AstraZeneca vaccine is cheaper and easier to use than vaccines by Pfizer and Moderna, the Associated Press reported. It has been approved for use in more than 50 countries and institutions, including the 27-member European Union and the World Health Organization. The U.S. has yet to approve the vaccine.
Several European countries previously suspended the use of the AstraZeneca vaccine in response to the reported blood clots, but many have resumed using it after the EMA announced on March 18 that it is a "a safe and effective vaccine."
The announcement by the EMA came shortly after a German independent vaccine expert panel reported that due to the reports of blood clots, the AstraZeneca vaccine should not be used in patients under age 60.
"At present the review has not identified any specific risk factors, such as age, gender or a previous medical history of clotting disorders, for these very rare events. A causal link with the vaccine is not proven, but is possible and further analysis is continuing," the EMA wrote in a statement on March 31.
For more reporting from The Associated Press, see below.
Cavaleri was asked how he could arrive at such a causal conclusion given the relatively few cases of adverse events.
"Among those vaccinated there is a number of cerebral thromboses with a low level of platelets among young people that is higher than what we would have expected. This we have to say," he was quoted as saying.
But he stressed the risk-benefit analysis remained positive for the AstraZeneca jab, even for young women who appear to be more affected by the clots.
"Let's not forget that young women also end up in intensive care with COVID. So we need to do very meticulous work to understand if the risk-benefit analysis remains for all ages," he was quoted as saying.
He said the EMA was in a difficult situation, given the different virus outbreaks in each of the EU's 27 nations.
"Certainly, many people would like EMA to resolve the question for everyone, but it's not that easy," he said. "Let's not forget that the weight of COVID is different in various countries. In Italy there are still around 500 people dying a day, in Norway nearly no one. These factors justify a different approach."
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