The first people have been injected as part of human trials in the UK for a coronavirus vaccine.
Both participants – a scientist and a cancer researcher – said they wanted to help in what could be a groundbreaking development in the fight against the disease.
Researchers from the University of Oxford administered the first dose on Thursday, while another was given a meningitis vaccine, used in the trial for comparison.
Microbiologist Elisa Granato, who took part in the trial on her 32nd birthday, said she was “excited” to support the efforts by volunteering.
She told the BBC: “Since I don’t study viruses, I felt a bit useless these days, so I felt like this is a very easy way for me to support the cause.”
Cancer researcher Edward O’Neill said: “It seems like the right thing to do to ensure that we can combat this disease and get over it a lot faster.”
Professor Sarah Gilbert, who is leading the team, said she is optimistic about the chances of success.
She said: “Personally, I’m very optimistic it’s going to work. Formally, we are testing it in an efficacy setting.
“There’s absolutely no suggestion we’re going to start using this vaccine in a wider population before we’ve demonstrated that it actually works and stops getting people infected with coronavirus.”
The Oxford Vaccine Group hopes to repeat the process with six more volunteers on Saturday, moving to larger numbers on Monday.
Up to 1,102 participants will be recruited across multiple study sites in Oxford, Southampton, London and Bristol.
In a tweet on Thursday night, Oxford University said: “Today @OxfordVacGroup began trialling a #Covid19 vaccine in two healthy human volunteers, to provide info on its safety & ability to generate good immune responses.
“We’re so grateful to the volunteers & researchers working tirelessly to develop this.”
Lydia Guthrie, who will begin taking part in the Oxford vaccine trial in a week, told BBC Radio 4’s The World At One programme: “They’ve (the clinical team) been very clear with participants about the potential risk, and vaccine trials are very carefully regulated, so we’ve had to give explicit consent at every step of the way.
“They’re really clear with us that as participants we can pull out at any time if we change our minds.”
She added that after receiving either the Covid-19 vaccine candidate or the meningitis jab, she would go about her normal life, keeping a diary about how she feels, or any symptoms.
John Jukes, from Witney, Oxfordshire, is expected to get his injection on Monday.
He told the Daily Mail: “I don’t see what I am doing as being heroic at all. I’m in a position to possibly be helpful to lots of people – that’s an opportunity to grab.”
A Covid-19 vaccine is considered the ultimate exit strategy by many experts, and scientists across the world are racing to develop one that can be produced at scale.
The Oxford team hopes to have at least a million doses of its candidate ready in September.
Another institution hoping to have a vaccine ready for use by the end of the year is Imperial College London.
The researchers say a vaccine may be available for frontline workers and the most vulnerable by late winter, with clinical trials starting in June.