The first results of the Oxford University vaccine trial are expected to be published today.

The vaccine, developed in conjunction with AstraZeneca, is already in large-scale human trials to assess whether it can protect against Covid-19.

However, its developers have yet to report the results of initial phase one testing, which would indicate if it is safe and whether it triggers an immune response. That data is expected to be published in The Lancet medical journal later.

Most experts think a vaccine is likely to become widely available by mid-2021. A vaccine would normally take years, if not decades, to develop - so that would be a huge scientific feat.

But there are no guarantees it will work. Four coronaviruses already circulate in human beings. They cause common cold symptoms and we don't have vaccines for any of them.