Results of the trial are expected to be published in The Lancet medical journal next week, Oxford said in a statement
Hopes of an effective COVID-19 vaccine being developed in the near future have been raised after two separate studies showed potential positive results, British media reported Thursday.
A University of Oxford trial showed its prototype vaccine generated an immune response against the virus, the reports said.
Blood samples taken from a group of some 1,000 volunteers who were given the vaccine stimulated antibodies and "killer T-cells", according to the Daily Telegraph newspaper.
Previous research has shown that T-cells can remain in the body for years and help fight viruses.
Results of the trial are expected to be published in The Lancet medical journal next week, Oxford said in a statement.
The potential development comes after US biotech firm Moderna said on Tuesday it would start the final stage of human trials for its vaccine candidate on July 27.
It said it had had promising results from earlier testing. Up to 30,000 Americans are expected to take part in the trials.
Moderna is considered to be in a leading position in the global race for a vaccine. Its study is set to run until October 2022 but preliminary results should be available before then.
The top US infectious diseases official, Anthony Fauci, has called the Moderna results "really quite good news".
The studies are the latest to inspire hopes of developing a vaccine after nearly 600,000 deaths and 13.4 millions cases worldwide since the outbreak began in China last year.
Meanwhile, a third group, BioNTech, a German company in partnership with US pharma giant Pfizer, plans to carry out its own trials on a vaccine involving 30,00 people.