Updated 4/7 at 11:30 CT
LONDON (AP) — The European Union drug regulator said Wednesday that it found a “possible link” between the AstraZeneca coronavirus vaccine and a rare clotting disorder but declined to impose any new age restrictions, saying the benefits of the shot still outweigh risks. Its U.K. counterpart, however, said it would offer people under 30 the choice of another product.
The European Medicines Agency described the clots as “very rare” side effects. It said most of the cases reported have occurred in women under 60 within two weeks of vaccination — but based on the currently available evidence, it was not able to identify specific risk factors. Experts reviewed several dozen cases that came mainly from Europe and the United Kingdom, where around 25 million people have received the AstraZeneca vaccine.
“The reported cases of unusual blood clotting following vaccination with the AstraZeneca vaccine should be listed as possible side effects of the vaccine,” said Emer Cooke, the agency's executive director.
But it placed no new age restrictions on using the vaccine in people 18 and over, as some countries have done.
“The risk of mortality from COVID is much greater than the risk of mortality from these side effects.,” Cooke said.
Dr. June Raine, the head of Britain’s Medicines and Healthcare Products Regulatory Agency, echoed that sentiment, saying that the benefits “continue to outweigh the risks for the vast majority of people.”
She called the unusual clots a “potential side effect” of the vaccine and said the evidence was “firming up,” but more study was needed to be sure.
The EMA, the World Health Organization and numerous other health authorities have said repeatedly that the AstraZeneca vaccine is safe and effective and that the protection it offers against COVID-19 outweighs the small risks of rare blood clots.
The announcements could have far-reaching effects on the use of the shot that is key to global efforts to end the pandemic.
The EMA's investigation was particularly focused on two types of rare blood clots: one that appears in multiple blood vessels and another that occurs in a vein that drains blood from the brain. It also evaluated reports of people who had low levels of blood platelets, which puts them at risk of severe bleeding.
As recently as last week, the EMA said “there is no evidence that would support restricting the use of this vaccine in any population” — a response to several countries doing just that — though an expert said more brain clots were being reported than would be expected.
Marco Cavaleri, head of health threats and vaccine strategy at the Amsterdam-based agency, told Rome's Il Messaggero newspaper on Tuesday that the European Union's medicines regulator is preparing to make a more definitive statement on the topic this week.
Based on the evidence so far, Cavaleri said there's a clear association between the AstraZeneca vaccine and the dozens of rare blood clots that have been reported worldwide amid the tens of millions of AstraZeneca shots that have been given out.
"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 platelets," Cavaleri was quoted as saying.
On Tuesday, AstraZeneca and Oxford University, which developed the vaccine, paused a study of the shot in children while the U.K. regulator evaluates the link between the shot and rare blood clots in adults.
"Whilst there are no safety concerns in the pediatric clinical trial, we await additional information" from the British regulator, an Oxford spokesperson said in a statement.
In Geneva, the World Health Organization said its experts were also evaluating a possible link between the AstraZeneca vaccine and rare blood clots — and that it might have a "fresh, conclusive assessment" before Thursday.
In March, more than a dozen countries, including Germany, suspended using AstraZeneca over the blood clot issue. Most EU nations restarted on March 19 — some with age restrictions — after the EMA said the benefits of the vaccine outweighed the risks of not inoculating people against COVID-19. At the time, the EMA recommended the vaccine's leaflet be updated with information about the rare clots.
Any further doubts about the AstraZeneca vaccine would be a setback for the shot, which is critical to Europe's immunization campaign and a linchpin in the global strategy to get vaccines to poorer countries. The AstraZeneca vaccine is cheaper and easier to use than rival vaccines from Pfizer and Moderna and has been endorsed for use in over 50 countries, including by the 27-nation EU and the World Health Organization. U.S. authorities are still evaluating the vaccine.
Cavaleri said while EMA was prepared to declare a link, further study was still needed to understand why and how the phenomenon occurs.
He said the rare blood clots, including some in the brain, coupled with a low level of blood platelets that may make people at risk of serious bleeding, "seem to be the key event to study further." Cavaleri promised more details soon, adding: "In the coming hours, we will say that the link is there, how this happens we still haven't figured out."
Cavaleri said the biological mechanism for how the vaccine might be causing the rare clots was still unknown and if it was linked to how the shot is made, other vaccines with similar technologies might also need to be evaluated.
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 ruled out a preventive therapy to address the rare blood clots, saying there is still too much unknown about the phenomenon.
Even after the March 19 restart, the Dutch and German governments suspended the jabs for people under 60 and some Europeans have been shying away from getting a shot.
Romania's national vaccination committee's chief, Valeriu Gheorghita, said Tuesday that since March, 207,000 people in Romania had canceled their AstraZeneca vaccine appointments and another 92,000 simply didn't show up.
"It is a high percentage, a third of people scheduled who did not show up," Gheorghita told reporters.
British Prime Minister Boris Johnson declined to be drawn directly into the latest warnings about the vaccine but urged people to look at the advice from Britain's independent Medicines and Healthcare Regulatory Agency.
"Their advice to people is to keep going out there, get your jab, get your second jab," he said during a visit Tuesday to an AstraZeneca facility in Macclesfield, in northwest England.
Last week, Britain's MHRA said seven people had died in the U.K. due to blood clots after getting the AstraZeneca jab. It said it wasn't clear if the shots are causing the clot and that it was undertaking a "rigorous review" into the reports. The agency said it had identified 30 blood clot cases out of 18.1 million AstraZeneca jabs given by March 24.
Adam Finn, a professor of pediatrics at the University of Bristol, said the latest surge of COVID-19 cases that is filling up hospitals across Europe should prompt people to get vaccinated as soon as possible.
"If you are currently being offered a dose of Oxford-AstraZeneca vaccine, your chances of remaining alive and well will go up if you take the vaccine and will go down if you don't," he said.