CNBC reports that a vaccine for Covid-19 will not be ready until the end of next year, according to Dale Fisher, chair of the World Health Organization (WHO) Global Outbreak Alert and Response Network.

That timeline would be a "very reasonable" expectation because of the necessary Phase 2 and 3 trials of any vaccine to guarantee both safety and efficacy, Fisher explained. There would also need to be a ramp up in production and distribution, as well as actually administering the vaccine, he said.

Fisher said "we are currently on target" for a vaccine in 2021 with five Phase 1 studies currently underway.

"We've always felt that by about April, May, we would be in Phase 1 studies, so this means a potential vaccine has been invented if you like; we're now trying it on individuals, basically to see if it's safe," Fisher told CNBC.

The current trials would allow "early collection of data" to assess whether the potential vaccine "actually works," before larger trials on safety and efficacy could be carried out, said Fisher, who is also a senior consultant at the infectious disease division at the National University Hospital in Singapore.

Fisher also said President Donald Trump's comments on Sunday - that he was confident a coronavirus vaccine would be developed by the end of 2020 - were "a bit premature."