Clinical trials of a potential COVID-19 vaccine are underway in Britain as other vaccine developers across Europe step up work on experimental doses against the disease caused by coronavirus.

Key points: Two volunteers have become the first people in the world to receive a potential COVID-19 vaccine

Two volunteers have become the first people in the world to receive a potential COVID-19 vaccine Up to 100 potential vaccines are under development globally

Up to 100 potential vaccines are under development globally The scientist in charge of the project said she is feeling confident about the trial

Two volunteers were the first people in the world to get a potential vaccine at Oxford University and the scientist in charge of the project said she was very optimistic it would be a success.

Edward O'Neill and Elisa Granato received a shot of ChAdOx1 nCoV-19.

Meanwhile other companies in Europe, including Italy's ReiThera, Germany's Leukocare and Belgium's Univercells said they were working together on another potential shot and aimed to start trials in a few months.

As many as 100 potential COVID-19 candidate vaccines are now under development by biotech and research teams around the world, and at least five of these are in preliminary testing in people in what are known as Phase 1 clinical trials.

The Oxford scientists said last week that large-scale production capacity was being put in place to make millions of doses of the ChAdOx1 nCoV-19 shot even before trials show whether it would be effective.

The European Union's drug regulator reiterated a warning against using two older malaria drugs outside of trials or national emergency use programs, citing potentially lethal side effects. ( AP: Kirsty Wigglesworth )

They said on Thursday the main focus of initial tests was "to find out if this vaccine is going to work against COVID-19, if it won't cause unacceptable side effects and if it induces good immune responses".

Oxford University professor of vaccinology Sarah Gilbert said given the success of other vaccine projects she had worked on, she was confident this one would also prove viable.

"I have a high degree of confidence about this vaccine because it is technology that we have used before," Professor Gilbert said.

"Of course we have to test it, of course we have to get the data from humans. We have used the technology to make lots of different vaccines though and we have done quite a number of, what we call, challenge studies using animals."

The race for a vaccine has been fuelled by the shortage of options for treating the disease.

The European Union's drug regulator reiterated a warning against using two older malaria drugs outside of trials or national emergency use programs, citing potentially lethal side effects.

Reuters