https://www.scientificamerican.com/article/scientists-react-to-halt-of-leading-coronavirus-vaccine-trial/

Enrolment in global trials of a leading coronavirus-vaccine candidate are on hold after a ‘suspected adverse event’ in a person who received the vaccine in the United Kingdom. Scientists say that it’s too soon to say what impact this might have on the global push to develop a vaccine, but that the news highlights the importance of waiting for the results of large, properly designed trials to assess safety before approving a vaccine for widespread use.

Researchers at the University of Oxford, UK, in collaboration with the pharmaceutical company AstraZeneca, are developing the vaccine, which is one of nine coronavirus vaccines in the final, ‘phase III’ stage of being tested.