A single dose of Oxford vaccine resulted in a four-fold increase in antibodies to the virus's spike protein in 95 per cent of participants one month after injection, AstraZeneca said in a statement.
Experts have given different timelines for when a potential vaccine would be ready, stating that it could be as early as next year. This was done so that the vaccine resembles the coronavirus and the immune system can learn how to attack it. The company said that data showed their experimental vaccine was safe and that it induced an immune response.
AstraZeneca's is among the leading vaccine candidates against COVID-19, that has claimed more than 600,000 lives worldwide, alongside others in mid and late-stage trials.
The new trial included 1,077 healthy adults aged 18 to 55 years with no history of COVID-19.
The UK government has signed deals for 90 million doses of promising coronavirus vaccines that are being developed, the media reported on Monday. "This vaccine is meant to induce both, so it can attack the virus when it's circulating in the body, as well as attacking infected cells", said the study's lead author, Prof Andrew Pollard.
The company has said it will not seek to profit from the vaccine during the pandemic.
Oxford scientists behind the trial have said the preliminary results are "very encouraging", while Boris Johnson has said it is an "important step in the right direction".
The two are among a handful of vaccines that have shown promise in human testing and gear up for late-stage trials, along with projects involving Moderna, BioNTech, and Inovio Pharmaceuticals.
All in all, the study found there were no serious adverse effects reported in people who received the vaccine.
If the Oxford vaccine proves to be successful, it could provide enough doses for frontline health and social care workers and people in greater danger of dying if they become infected.
Compared with the control group of those given a meningitis vaccine, the COVID-19 vaccine caused minor side effects more frequently, according to the study.
Some can provoke an immune response, but none has yet been proven to protect against infection.
More than 150 possible vaccines are being developed and tested around the world to try to stop the novel coronavirus pandemic.
"The fact remains we may never get a vaccine and if we do get one, we have to be prepared that it may not be a vaccine which prevents getting the virus, but rather one that reduces symptoms", she said.