OXFORD trials for a Covid-19 vaccine are back on after being suspended for an investigation.

A volunteer had reportedly suffered potentially dangerous side effects.

In a statement, Oxford University said: “The ongoing randomised controlled clinical trials of the Oxford coronavirus vaccine CHAdOx1 nCoV-19 will resume across all UK clinical trial sites.

“Globally some 18,000 individuals have received study vaccines as part of the trial. In large trials such as this, it is expected that some participants will become unwell and every case must be carefully evaluated to ensure careful assessment of safety.

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“On Sunday our standard review process triggered a study pause to vaccination across all of our global trials to allow the review of safety data by an independent safety review committee, and the national regulators. All routine follow-up appointments continued as normal during this period.

“The independent review process has concluded and following the recommendations of both the independent safety review committee and the UK regulator, the MHRA, the trials will recommence in the UK.

“We cannot disclose medical information about the illness for reasons of participant confidentiality. We are committed to the safety of our participants and the highest standards of conduct in our studies and will continue to monitor safety closely.”

AstraZeneca, which is developing the vaccine with the university, issued a statement on Tuesday night saying the late-stage studies of the vaccine had been paused while the company investigated whether the patient’s reported side effect was connected with the vaccine.

The vaccine is being tested on thousands of people in Britain and the US, and in smaller study groups in Brazil and South America.