Updated 5.15pm
The EU's drug regulator said Wednesday that blood clots should be listed as a "very rare" side effect of the AstraZeneca coronavirus vaccine but that the jab's benefits continue to outweigh the risks.
“The benefits are well-established and the risks are very rare,” the chair of the European Medicines Authority's Pharmacovigilance Risk Assessment Committee, Sabine Straus, said.
No specific risk factors, including age, have been identified for thrombosis with the AstraZeneca shot, which could stem from an immune response, the EMA said.
The watchdog's findings come after several countries halted the use of the vaccine following dozens of cases of people with clots in blood vessels draining from the brain after receiving jabs, some of them fatal.
Around 34 million people have received the vaccine in the European Economic Area and United Kingdom. Of those, there have been 169 reported cases of cerebral venous sinus thrombosis and 53 cases of splanchnic vein thrombosis. Both are rare kinds of blood clots.
Malta is currently administering the vaccine to people aged under 70. Health Minister Chris Fearne has said that there have been no blood clotting cases reported locally.
"EMA's safety committee has concluded today that unusual blood clots with low blood platelets should be listed as very rare side effects" of the AstraZeneca jab, the Amsterdam-based watchdog said in a statement.
But it stressed that it believed people should continue to take the vaccine as part of the battle against the disease.
"The safety committee has confirmed that the benefits of the AstraZeneca vaccine in preventing COVID-19 overall outweigh the risk of side effects," EMA chief Emer Cooke told a news conference.
"It is saving lives."
The EMA's head of data analytics Peter Arlett drew a comparison between the AstraZeneca vaccine to the contraceptive pill, which can also cause blood clotting in rare instances.
The EMA said that the AstraZeneca vaccine's product information will be updated to include mention of blood clotting as a rare side effect together with a warning noting some of its early symptoms, such as a persistent headache, blurred vision or bruising in areas of the body not affected by the injection.
No confirmed link to gender, age yet
Despite the fact that many of the cases have been reported in women under 55, prompting a number of countries to restrict the vaccine's use to older people, the regulator said it had not been able to pinpoint those at risk.
"Specific risk factors such as age, gender or medical history have not been able to be confirmed, as the rare events are seen in all ages," Cooke said.
"A plausible explanation for these rare side effects is an immune response to the vaccine."
UK to offer under-30s different vaccine
Canada, France, Germany and the Netherlands are among several countries that are not recommending the shot for younger people.
Britain, which has made extensive use of the AstraZeneca vaccine, said on Wednesday that people under 30 would be offered an alternative vaccine.
EMA director Cooke noted that the UK had more data to work with as more young people have received the vaccine there.
"We will take this into account in our further evaluations," she said.
AstraZeneca's vaccine has been administered in at least 111 countries, more than any of its rivals. It is being used in wealthier countries and poor nations, largely as part of the WHO-backed Covax scheme to ensure equitable access to vaccines.
The controversy surrounding the jab has marred a global vaccine rollout that governments hope will help countries emerge from a pandemic that has ravaged the global economy and subjected much of humanity to some form of confinement.