The UK’s first human trials for a coronavirus vaccine began on Thursday at the University of Oxford.
The trials on 500 people will first focus on safety and toleration and will give an initial assessment of how effective the vaccine is in immunising against Covid-19.
Half of the people in the trial will have the Covid-19 vaccine and half will have one for meningitis, but none will know which they have.
Over time, they will return to the university labs to be tested.
The trial is on a drug based on a chimpanzee adenovirus modified to produce a protein from the coronavirus.
Adenoviruses are a group that infect the eyes, respiratory system, intestines, urinary tract and nervous system.
The Oxford team, led by Prof Sarah Gilbert, worked on a vaccine for the Ebola outbreak in West Africa in 2014.
Prof Gilbert said that if the study were successful, more extensive research could be conducted and that a million doses of the vaccine may be ready as early as September.
British Health Secretary Matt Hancock on Wednesday praised the team for its quick progress that in normal times would take years.
The government has given £20 million (Dh91m/US$25m) to the university’s team and a further £22.5m to Imperial College, where another Covid-19 vaccine is being developed.
The Imperial team is set to begin human trials in June.
"It's fantastic to see the research team at the University of Oxford get this vaccine trial up and running in record time," said Arne Akbar, president of the British Society for Immunology.
“The UK leads the world for the quality of our immunology research.
"This is another great example of how the community has come together to drive forward scientific discovery into this pandemic, and to work towards developing a safe and effective vaccine.”
But Mr Akbar said that developing a vaccine for the coronavirus would not be easy and it was crucial that scientists had an in-depth understanding of the exact immune response to the coronavirus.
"All vaccine candidates will still need to go through many stages of testing to ensure that they are safe and effective for wide-scale use," he said.
"We need to be realistic about the timescale in which this can take place.
"We also know that everyone’s immune system functions differently. Older people in particular often generate less potent and long-lasting immune responses to vaccination.
"As this group is particularly vulnerable to Covid-19, we also need to keep supporting research efforts into other approaches, including developing new medicines and repurposing existing drugs that may be effective treatments for patients with Covid-19.
“Well done to the Oxford team and despite all the notes of caution, we sincerely hope the vaccine works."
Prof Gilbert was optimistic, but also warned there was no guarantee the vaccine on which she was working would be effective.
“That’s why we have to do trials to find out," she told the BBC. "The prospects are very good but clearly not completely certain."
Prof Gilbert called on the government to help support the rapid production of the vaccine, should it be proven to be effective.
On Friday, the government began a large-scale test on about 20,000 households in England to help understand the rate of infection and how many people were likely to have developed antibodies.
Those taking part will form a representative sample of the entire UK population, by age and geography. The results are expected in early May.
Meanwhile, the global opinion of whether it is safer to wear medical face masks in public to battle the coronavirus remains divided.
British government scientists were expected to recommend on Thursday that the public should not wear surgical face masks but could choose to wear a scarf or face covering.
The advice echoes that of the World Health Organisation, which says there is little evidence that wearing a mask in the community stopped healthy people from picking up respiratory infections.
Instead, they say it might make more sense for someone to wear a mask if they are coughing and showing coronavirus symptoms.
But Germany, which has won praise for its response to Covid-19, on Wednesday advised to make face masks compulsory on public transport and when shopping, to combat the spread of the virus.