The World Health Organization's vaccine safety experts were due to meet Tuesday to discuss the Oxford-AstraZeneca Covid-19 vaccine, as the list of countries temporarily halting its rollout over blood clot concerns continued to grow.
On Tuesday, Cyprus, Luxembourg, Latvia and Sweden became the latest European nations to suspend its use, despite advice from international medical agencies that the benefits of getting shots into arms outweigh any potential risks.
WHO on Monday appealed to countries to keep vaccination campaigns going, saying there was no evidence the vaccine caused clotting issues.
"As of today, there is no evidence that the incidents are caused by the vaccine and it is important that vaccination campaigns continue so that we can save lives and stem severe disease from the virus," WHO spokesman Christian Lindmeier said.
WHO is assessing the latest reports of thromboembolic events, but said it was "unlikely" to change its recommendations.
Europe's medicines regulator, the European Medical Authority (EMA), which authorized the use of the shot for the 27-nation bloc, is convening a special meeting Thursday to review information gathered into whether the AstraZeneca vaccine influenced clotting in vaccinated people. The EMA has also advised against halting vaccination campaigns while investigations are ongoing.
But much of Europe has gone against that advice in recent days, temporarily halting AstraZeneca shots even as the continent confronts a third wave of the pandemic, spurred by variants of the virus, and faces criticism over sluggish vaccination campaigns.
Denmark was the first to press pause on the AstraZeneca vaccine Thursday as a "precautionary measure" while Danish health officials investigate potential side effects after one person who developed a blood clot after vaccination died. Norway, Iceland and Bulgaria quickly followed suit.
The Danish woman who died after vaccination had a low number of platelets, blood clots in small and large vessels and bleeding, according to the Danish Medicines Agency.
"The clinical picture is highly unusual and is currently being thoroughly investigated by the European Medicines Agency," the agency said in a statement on Monday.
Another death was reported in Norway on Monday, along with a handful of non-fatal cases with similar "unusual" adverse reactions, the Norwegian Medicines Agency said. The agency has received over 1,000 reports of side effects in recent days, which it said it is currently reviewing.
AstraZeneca, meanwhile, has doubled down on the safety of its vaccine. In a statement on Sunday, the pharmaceutical giant said that of the 17 million people vaccinated in the European Union and the United Kingdom so far, blood clot incidents were "much lower than would be expected to occur naturally in a general population."
Still, Spain, Germany, France, Italy, Portugal, Ireland, the Netherlands and Indonesia have joined countries halting AstraZeneca vaccinations.
Most countries to issue a suspension of the vaccine have acknowledged there is no evidence yet that the AstraZeneca shots had caused the blood clots.
The AstraZeneca vaccine, which was authorized for use by the WHO in February, is seen as key to fighting the coronavirus in lower- and middle-income countries because it is cheap and easy to store. Those two factors have made it a lynchpin for rollout plans globally. And fears are growing that the handling of blood clot reports will impact vaccine confidence.
The chief investigator on the Oxford-AstraZeneca vaccine trial, Andrew Pollard, warned it was "absolutely critical" people weren't put off from receiving the vaccination as countries in Europe see a third surge in infections. He said it appears from the data received from regulators there was "no signal of a problem."
"It's absolutely critical that there is careful evaluation of these cases, they've obviously been flagged in a couple of countries around Europe, so they need to be looked at very closely to see if there's anything unusual about them ... but in the meantime, we really need to make sure that people are protected against Covid," Pollard said in an interview on BBC Radio 4's Today program.
Britain's medicines regulator on Monday said it had not seen any uptick in blood clots in the UK, where more than 11 million doses of AstraZeneca have been administered.
The UK, where the Oxford-AstraZeneca vaccine was developed and is being manufactured, is among a number of countries that are still sticking with the shot. Belgium, Australia, Poland, Nigeria, Mexico and the Philippines have said they will continue to use the vaccine as investigations progress.
After becoming the first country outside Europe to delay its rollout of the Oxford-AstraZeneca vaccine, Thailand said on Monday that it would continue to receive doses.
Thailand's Prime Minister Prayut Chan-o-cha and members of his cabinet received their first shots of the vaccine on Tuesday, broadcast in a live stream.
"This will build confidence among the general public to receive vaccinations arranged by the government," Prayut said after the inoculation.