"The experts will meet again on Thursday to come to a conclusion and to advise whether there are any further actions that need to be taken," Cooke said at an online news conference. But she noted that there was no evidence that the incidents had been caused by the vaccine at the moment.
"A situation like this is not unexpected when you vaccinate millions of people," she said.
Cooke stressed the need to take the time to evaluate every reported case and come up with a "science-based" assessment.
"The benefits continue to outweigh the risks, but this is a serious concern and it does need serious and detailed scientific evaluation. This is what we are involved in at the moment," Cooke said.
Sweden joins growing list of countries that have halted distribution of AstraZeneca jab
Some 24 countries have temporarily halted, or promised to halt, distribution of the AstraZeneca jab with Sweden becoming the latest European country to join them on Tuesday.
No cases of severe blood clots had been reported in Sweden, but neighboring Norway and Denmark had each reported one death. (Related: Eight European nations pause AstraZeneca coronavirus vaccinations after reports of "serious" blood clot.)
Thailand, on the other hand, initially suspended the use of AstraZeneca vaccine, but the country's health authorities later decided to go ahead with it.
The World Health Organization (WHO) criticized the decision to halt vaccinations because it could potentially undermine global perceptions of vaccine safety.
But France's Industry Minister Agnès Pannier-Runacher didn't agree with the WHO in her statement before Tuesday's online news conference. She said that that the countries had acted in an effort to help protect public confidence.
"It is important that there is no distrust in the population," Pannier-Runacher said. "If you see decisions being made in other countries, the risk is that a mistrust of the vaccine could develop. Our intention is to be perfectly transparent...and [show] that every time that there is an alert, we treat it as professionally as possible."
Later on Tuesday, the EU's health ministers held a video call where they shared information about their concerns on the side effects of the AstraZeneca vaccine.
Following the online news conference, Italian Prime Minister Mario Draghi and French President Emmanuel Macron said they were ready to restart AstraZeneca jabs as soon as Europe's top medical regulator officially declared its safety review to be over.
Italian Medicines Agency (AIFA) Director Nicola Magrini earlier told an Italian newspaper that the decision by Germany, France and Italy to suspend the shots after reports of dangerous side effects was a "political one."
"We got to the point of a suspension because several European countries, including Germany and France, preferred to interrupt vaccinations...to put them on hold in order to carry out checks. The choice is a political one," Magrini said.
Magrini insisted the AstraZeneca vaccine was safe and that the benefit-to-risk ratio of the jab is "widely positive." There have been eight deaths and four cases of serious post-vaccination side effects in Italy.
Meanwhile, in Germany, a meeting of state and federal leaders where the country's vaccine strategy was due to be discussed had been moved to Friday. This is one day after the experts are expected to wrap up their safety review of the AstraZeneca jab.
Rare side effects are not exactly rare with AstraZeneca vaccine
The AstraZeneca vaccine has been heralded as a critical success in the fight against COVID-19 because it is cheap to develop, ship and store and it is using the adenovirus vector technology that has long been used for vaccines.
But its trial phase didn't go smoothly and featured a number of rare side effects. At one point last year, the United States halted its trial for a whole month. (Related: First DEATH reported in AstraZeneca COVID-19 vaccine trial, but human experimentation will continue anyway.)
Last week, Denmark reported "highly unusual" symptoms in a 60-year-old citizen who died from a blood clot after receiving the vaccine. In Norway, three health workers were treated in a hospital over the weekend for bleeding, blood clots and a low count of blood platelets after receiving the AstraZeneca vaccine. One of them died. Their cases were labeled "unusual symptoms" by health authorities.
No such cases had been found yet in the Netherlands, but the country still suspended the use of AstraZeneca's COVID-19 vaccine. The vaccine will not be used until at least March 29 as a precaution, the Dutch government said in a statement.
"We can't allow any doubts about the vaccine," Dutch health minister Hugo de Jonge said. "We have to make sure everything is right, so it is wise to pause for now."
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