The UK is pushing ahead to be the first nation to carry out "human challenge" studies where up to 90 healthy people will be deliberately exposed to Covid.
The trials, which could begin in January, aim to speed up the race to get a Covid-19 vaccine.
The government is putting £33.6m towards the groundbreaking work.
Safety will be a number one priority, experts insist. The plans will need ethical approval and sign-off from regulators before they can go ahead.
Human challenge studies provide a faster way to test vaccines because you don't have to wait for people to be exposed to an illness naturally.
Researchers would first use controlled doses of the pandemic virus to discover what is the smallest amount that can cause Covid infection in volunteers aged 18 to 30.
These human guinea pigs, who will be infected with the virus through the nose and monitored around the clock, have the lowest risk of harm due to their young age and good health.
Next, scientists could test if a Covid vaccine prevents infection.
Lead researcher for the project Dr Chris Chiu, from Imperial College London, said: "My team has been safely running human challenge studies with other respiratory viruses for over 10 years. No study is completely risk free, but the Human Challenge Programme partners will be working hard to ensure we make the risks as low as we possibly can."
Prof Peter Openshaw, co-investigator on the study and director of the Human Challenge Consortium, said deliberately infecting volunteers with a known human pathogen was "never undertaken lightly".
"However, such studies are enormously informative.
"It is really vital that we move as fast as possible towards getting effective vaccines and other treatments for Covid-19."
There are hundreds of Covid vaccines being developed around the world and several front-runners already in the final stages of testing, including one from Oxford University.
While some of these could get results and start to be used before the new trial has chance to begin, researchers say the work will still be useful, particularly for head-to-head studies to compare which vaccines work best.
Experts say we will probably need a few different vaccines, as well as effective treatments, to defeat Covid. They will also need to be tested in those at highest risk from Covid – the elderly and vulnerable.
The first stage of the human challenge project will be delivered by a partnership between Imperial College London, the Royal Free Hospital's specialist and secure research unit in London and a company called hVIVO.
After exposure to Covid, the young volunteers will need to stay in a biosecure facility until they are no longer infectious.
They will be financially reimbursed for their time, and monitored for up to a year after taking part in the study to check for any side-effects.
People can sign up here.
Purposely infecting someone with Covid does pose an ethical dilemma, especially since there is no treatment to cure patients, although there are ones that might make it less deadly.
Prof Julian Savulescu, an expert in ethics at Oxford University, said the trials were justified: "In a pandemic, time is lives. So far, over a million people have died.
"There is a moral imperative to develop to a safe and effective vaccine – and to do so as quickly as possible.
"Given the stakes, it is unethical not to do challenge studies."
Business Secretary Alok Sharma said: "We are doing everything we can to fight coronavirus, including backing our best and brightest scientists and researchers in their hunt for a safe and effective vaccine."