Denmark has become the first country in the world to stop using the Oxford-AstraZeneca's vaccine altogether over a potential link to a rare but serious form of blood clot.

Health authorities in the Scandinavian nation admitted the decision would delay the conclusion of its vaccination scheme to early August from 25 July.

But even that new timeline assumes it will start using the Johnson & Johnson vaccine, whose rollout in Europe has been delayed over similar clotting concerns and the use of which Denmark has suspended.

That jab comprises around a third of the country's total contracted supply.

Danish health agency head Soren Brostrom told a news briefing that results of investigations into the AstraZeneca-associated blood clots "showed real and serious side-effects".

"We have therefore chosen to continue the vaccination programme for all target groups without this vaccine," he said.

Astrazeneca said it respected Denmark's choice and that would continue to provide it with data to inform future decisions.

The EU's drug watchdog said last week it had found a possible link between the vaccine and cerebral venous sinus thrombosis (CVST), a brain blood clot.

However, while it left the final decision to individual states, it said the risk of dying from COVID-19 was much greater than the risk of mortality from rare side effects.