AstraZeneca Vaccine Trial: AstraZeneca announced on Wednesday it had "voluntarily paused" its trial of the vaccine developed alongside Oxford University after the volunteer developed an unexplained illness.
On Tuesday, the studies were being paused while it investigated whether the adverse reaction was linked with the vaccine.
But on Saturday, the university said it had been deemed safe to continue.
"This pause shows we will always put safety first. We will back our scientists to deliver an effective vaccine as soon as safely possible," he added.
The university said in a statement that it was "expected" that "some participants will become unwell" in large trials such as this one.
The World Health Organization (WHO) says nearly 180 vaccine candidates are being tested around the world but none has yet completed clinical trials.
Hopes have been high that the vaccine might be one of the first to come on the market, following successful phase 1 and 2 testing.
Its move to Phase 3 testing in recent weeks has involved some 30,000 participants in the US as well as in the UK, Brazil and South Africa. Phase 3 trials in vaccines often involve thousands of participants and can last several years.