Vaccine official says there is a link between AstraZeneca’s shot and rare blood clots

A top vaccines official at the European Medicines Agency said on Tuesday that AstraZeneca’s vaccine was linked to blood clots in a small number of recipients, the first indication from a leading regulatory body that the clots may be a real, if extremely rare, side effect of the shot.

The agency itself has not formally changed its guidance, issued last week, that the benefits of the AstraZeneca vaccine outweigh the risks. It said on Tuesday that its review was ongoing and that it would announce its findings this week. But any further ruling from regulators would be a setback for a shot that Europe and much of the world are relying on to save lives amid a global surge in coronavirus cases.

The medicines agency said last week that no causal link between the vaccine and rare blood clots had been proven. Only a few dozen cases of blood clots have been recorded among the many millions of people who have received the vaccine across Europe.

But the vaccines official, Marco Cavaleri, told an Italian newspaper that “it is clear there is an association with the vaccine.” He said that it would likely remain up to individual countries to decide how to respond, given the variation in supply of COVID-19 vaccines and in the state of the virus.

Those comments represented the first indication from a member of a leading regulatory body that the blood clots could be a genuine, if extremely rare, side effect of the AstraZeneca vaccine. Previously, health officials in several European countries temporarily restricted the use of the shot in certain age groups, despite the European Medicines Agency’s recommendation to keep administering it.

Regulators in Britain and at the World Health Organization have also said that, while they were investigating any rare side effects, the shot was safe to use and would save many lives.

Cavaleri told the Italian newspaper Il Messaggero that European regulators had not determined why the vaccine might be causing the rare blood clots, which generated concern because the cases were so unusual. They involved blood clots combined with unusually low levels of platelets, a disorder that can lead to heavy bleeding.

The most worrisome of the conditions, known as cerebral venous sinus thrombosis, involves clots in the veins that drain blood from the brain, a condition that can lead to a rare type of stroke.

The clots are, by all accounts, extremely rare. European regulators were analysing 44 cases of cerebral venous sinus thrombosis, 14 of them fatal, among 9.2 million people who received the AstraZeneca vaccine across the continent. Emer Cooke, the European Medicines Agency’s director, said that the clotting cases in younger people translated to a risk for one in every 100,000 people under 60 given the vaccine. Younger people, and especially younger women, are at higher risk from the brain clots, scientists have said.

In Britain, regulators last week reported 30 cases of the rare blood clots combined with low platelets among 18 million people given the AstraZeneca vaccine, which was developed with the University of Oxford. No such cases were reported in people who had received the Pfizer-BioNTech vaccine in Britain.

Regulators in Britain have said that people should get the vaccine “when invited to do so.” But British news reports indicated Monday night that regulators were considering updating that guidance for certain age groups.