The practice is called a human-challenge study -- or controlled human infection study -- and it can truncate a conventional vaccine study by several months. (If the Covid-19 study comes to fruition, experts say it would likely be administered by nose drop.) JUST WATCHED What might happen when a Covid-19 vaccine is ready? Replay More Videos ... MUST WATCH What might happen when a Covid-19 vaccine is ready? On May 6, the World Health Organization released a report outlining "key criteria for the ethical acceptability of Covid-19 human challenge studies."

Source: CNN May 13, 2020 12:00 UTC