Final clinical trials for a coronavirus vaccine, developed by AstraZeneca and Oxford University, have been put on hold after a participant had a suspected adverse reaction in the UK. AstraZeneca described it as a “routine” pause in the case of “an unexplained illness”. The outcome of vaccine trials is being closely watched around the world. The AstraZeneca-Oxford University vaccine is seen as a strong contender among dozens being developed globally. A final decision on restarting the trial will be taken by the medical regulator the MHRA, which could take only days. But until then all international vaccination sites, in the UK, Brazil, South Africa and the USA are on hold. The Oxford University team believe this process illustrates that they are committed to the safety of their volunteers and the highest standards of conduct in their studies.