Oxford University researchers are planning to begin human trials of a vaccine this week

The government’s chief science adviser has warned against banking on a Covid-19 jab and added that “all new vaccines are a long shot”.

Oxford University researchers are planning to begin human trials of a vaccine this week, and believe that they could have results showing whether it works as early as September.

However, Sir Patrick Vallance, the chief scientific adviser, has cautioned that even if a vaccine shows signs of protecting against the virus, ensuring that it is safe could take considerably longer.

Sir Patrick Vallance said that developing a new vaccine presents “challenges” ANDREW PARSONS /EPA

“All new vaccines that come into development are long shots. Only some end up being successful,” he wrote. “Coronavirus will be no different and presents new challenges for vaccine development. This will take time.”

It came as the coronavirus death toll