The university authorities said such side effects are not totally unexpected, reports AP.
“In large trials it is expected that some participants will become unwell and every case must be carefully evaluated to ensure careful assessment of safety," it added.
According to the university, globally some 18,000 individuals have received study vaccines as part of the trial.
It wouldn't disclose the medical information about the illness for reasons of participant confidentiality but says it is "committed to the safety of our participants and the highest standards of conduct in our studies and will continue to monitor safety closely."
Also read: Coronavirus vaccine to be available by end of year: Chinese company
Health experts say pauses in drug trials are commonplace to ensure safety and effectiveness.