The phase one trial had more than 1,000 participants in people ages 18 to 55. The Oxford researchers said the vaccine produced antibodies and killer T-cells to combat the infection that lasted at least two months.

The vaccine was also found to be well-tolerated and there were no serious adverse event. Fatigue and headache were the most commonly reported side effects, the researchers said. Other common side effects included pain at the injection site, muscle ache, chills and a fever.

"The immune system has two ways of finding and attacking pathogens — antibody and T cell responses," Oxford professor Andrew Pollard said in a release earlier in the day. "This vaccine is intended to induce both, so it can attack the virus when it's circulating in the body, as well as attacking infected cells. We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period."