The second shot of the Covid-19 vaccine developed by AstraZeneca and the University of Oxford must not be given to anyone who has had blood clots with low blood platelets after receiving the first, Europe's medicines regulator has said.

The advice for healthcare professionals was provided by the European Medicines Agency (EMA) as part of an ongoing review into rare, but severe blood clots possibly linked to inoculation after the shot and also to Johnson & Johnson's coronavirus vaccine.

"While blood clots with low blood platelets following vaccination are very rare, EMA continues to advise people to be aware of symptoms ... so they can receive prompt specialised medical treatment if needed," the EMA said.

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