AstraZeneca says 'no evidence' of higher blood clots risk from Covid vaccine

"An analysis of our safety data of more than 10 million records has shown no evidence of an increased risk of pulmonary embolism or deep vein thrombosis in any defined age group, gender, batch or in any particular country" from the jab, a company spokesperson said.

"In fact, the observed number of these types of events are significantly lower in those vaccinated than would be expected among the general population."

The AstraZeneca jab, developed with Oxford University, forms the mainstay of Britain's vaccination programme, and of many developing economies. It is relatively cheap and easier to store than other jabs.

But it has been dogged by controversy in Europe, with some governments initially refusing to certify its use for people aged over 65 despite scientific advice finding no reason for limits.

This week Denmark, Norway and Iceland have paused their use as a precaution after isolated reports of recipients developing blood clots.

Italy and Austria have also banned the use of shots from separate batches, while Bulgaria and Thailand said they would delay its rollout.

However, the World Health Organization earlier Friday said there was no reason to stop using the Covid-19 vaccine, stressing there was no causal link between the jab and any clotting.

A range of health authorities has also insisted it is safe, including the European Medicines Agency.

British Prime Minister Boris Johnson's official spokesman told reporters on Thursday: "We've been clear that it's both safe and effective... and when people are asked to come forward and take it, they should do so in confidence."

Britain began the world's first mass vaccination drive against the coronavirus in December, underpinned largely by the Oxford-AstraZeneca jab and another from Pfizer-BioNTech.