An immunologist says it will be months before the Oxford vaccine could be developed.
The vaccine, developed by the British university, has been deemed safe and triggers an immune response in patients.
The early results of human trials have been published by The Lancet.
Professor Paul Moynihan, from NUI Maynooth, says it appears to work which is very positive news.
“It seems to be safe, so apart from some modest reactions like pain at the sight of infection, some fever, muscle ache, headache - but apart from that, there doesn’t seem to be any serious reaction.
“Importantly, the vaccine appeared to produce an immune response.”
Early results indicate the vaccine could provide double protection – generating an immune response which stimulates the body to produce both an antibody and T-cell response.
The vaccine – called ChAdOx1 nCoV-19 – uses a weakened version of a common cold virus (adenovirus) which causes infections in chimpanzees.
It has been genetically changed so it is impossible for it to grow in humans.
It is hoped the vaccine will make the body recognise and develop an immune response to the spike protein – recognisable in images of the virus – that will help stop Covid-19 from entering human cells and therefore prevent infection.
The results of the clinical trials, published in The Lancet on Monday, indicate that the vaccine candidate has triggered two responses in the immune system.
The first is that it stimulates the immune system to produce antibodies – proteins produced by the blood in response to antigens which are harmful substances that come from outside the body, such as from viruses or bacteria – and that it also causes the body to produce T-cells.
If the non-specific immune cells which respond to any invader instantly cannot tackle it, the T-cells come into play.
These cells attack the virus directly.
With questions remaining about the duration of the antibody response to Covid-19, research suggests T-cells have a more important role in offering protection against the disease.