The European Union’s medicines regulator has said there is “no indication” that AstraZeneca’s coronavirus vaccine is the cause of a reported increase in blood clots.
A growing number of countries across the world have suspended the use of the vaccine over concerns about its side effects.
Emer Cooke, European Medicines Agency (EMA) executive director, told a virtual press conference: "I want to also stress at present there is no indication that vaccination has caused these conditions.
"They have not come up in the clinical trials and they are not listed as known side events with this vaccine.
"In clinical trials, both vaccinated people and people who received the placebo have shown some very small number of blood clot developments.
"The number of thromboembolic events overall in vaccinated people seems not to be higher than that seen in the general population."
She added that the benefits of the Oxford/AstraZeneca Covid-19 jab outweighed the risks.
"Vaccines for Covid-19 help to protect individuals from becoming ill, especially healthcare professionals and vulnerable populations such as older people and people with chronic diseases," she said.
"This is a very important consideration in our assessment of the benefit-risk.
"So while the investigation is ongoing currently we are still firmly convinced that the benefits of the AstraZeneca vaccine in preventing Covid-19, with its associated risk of hospitalisation and death, outweigh the risk of these side effects."
She also told the virtual press conference that its experts will be meeting on Thursday to draw their conclusions on concerns about the Oxford/AstraZeneca jab.
"We have pulled together an ad hoc meeting again today to help us evaluate these cases with all the surrounding information that the member states will have," she said.
"The experts will then carry on their assessment and again will meet on Thursday to come to a conclusion on the full information that has been gathered and to advise us as to whether there are any further actions that need to be taken.
"We will inform the public of the outcome immediately after this meeting.
"Our experts are working tirelessly to carry out this assessment as quickly as possible, but it needs a scientific evaluation, we need to have the facts first, we cannot come to a conclusion until we have done a thorough scientific analysis and we owe it to the European citizens to deliver this clear and science-based response."
So far Austria, Bulgaria, Congo, Denmark, Estonia, France, Germany, Iceland, Indonesia, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Romania, South Africa, Sweden, Thailand and Venezuela have all suspended use of the of the Oxford/AstraZeneca Covid-19 jab.
More than 11 million Brits have had the Oxford-AstraZeneca jab which has sparked concern that they could face health issues.
But the head of the Oxford University vaccine group Professor Andrew Pollard said that while "safety is clearly absolutely paramount", about 3,000 cases of blood clots occur every month in the UK from other causes.
Prime Minister Boris Johnson's official spokesman said: "The Oxford/AstraZeneca vaccine remains both safe and effective, and we urge anybody asked to come forward to receive a vaccine to do so."
There was "no evidence" that blood clots are any more likely to occur following vaccination, the spokesman said.