Two volunteers in the UK were injected with the new vaccine, the first of more than 800 volunteers recruited for the study. Half of the volunteers will be injected with the Covid-19 vaccine, and half with a control vaccine which protects against meningitis. The volunteers will not know which vaccine they will get, but doctors will.

“I’m a scientist, so I wanted to try to support the scientific process wherever I can,” said Elisa Granato, the first volunteer who received the jab.

A team at Oxford University developed the vaccine in under three months. The pre-clinical research was led by Sarah Gilbert, professor of vaccinology at the Jenner Institute.

“Personally I have a high degree of confidence in this vaccine,” she said. “Of course, we have to test it and get data from humans. We have to demonstrate it actually works and stops people getting infected with coronavirus before using the vaccine in the wider population.”

How does the vaccine work?

The vaccine is made from a weaker version of the common cold virus from chimpanzees that has been modified so it can’t grow in humans.

HOW CORONAVIRUS VACCINE WILL WORK. PICTURE: BBC

The Oxford team has already developed a vaccine against another type of coronavirus called “Mers” which had positive results.

However, the only way for the team to know if the vaccine is effective is by comparing the number of people who get infected in the months ahead of the trial.

“We’re chasing the end of this current epidemic wave,” said Prof Andrew Pollard, director of the Oxford Vaccine Group, and leader of the trial. “If we don’t catch that, we won’t be able to tell whether the vaccine works in the next few months. But we do expect that there will be more cases in the future because this virus hasn’t gone away.”

The recruitment of healthcare workers will be prioritised due to them being more likely to be infected. In the coming months, a larger trial of about 5,000 volunteers will start and will have no age limit.

Researchers are evaluating whether the elderly might need two doses of the jab, as they tend to have a weaker immune response to vaccines.

Is the vaccine safe?

The volunteers will be carefully monitored in the next few months. They have been informed about possible side effects such as headaches, a sore arm or fevers in the first couple of days after the vaccination. They have also been informed about the possible risk of developing a serious reaction to coronavirus, which could be seen in some early Sars animal vaccine studies. However, the Oxford team says that based on the data, the risk of that happening is very low, and data from animal studies has been very positive.

Scientists are hoping to have as many as one million doses ready by September, and to produce even more if the vaccine works.