The efficacy depended on the dosing regimen, the university said in a statement, with the vaccine, which was developed with pharmaceutical company AstraZeneca, becoming 90% effective if administered at a half dose and then at a full dose and 62% effective if administered in two full doses.
There were no hospitalised or severe cases of the virus among those who received the vaccine, the university said in a statement.
A total of 131 participants came down with COVID-19 in the trial. The phase three trials include more than 23,000 participants in the UK and Brazil.
“These findings show that we have an effective vaccine that will save many lives. Excitingly, we’ve found that one of our dosing regimens may be around 90% effective and if this dosing regimen is used, more people could be vaccinated with planned vaccine supply,” said Professor Andrew Pollard, the chief investigator of the Oxford Vaccine Group.