RCT = randomised controlled trial - a trial where some test subjects are given the vaccine and some are given the vaccine, then you follow the subjects and see

RCT = randomised controlled trial - a trial where some test subjects are given the vaccine and some are given the vaccine, then you follow the subjects and see which ones get COVID and how bad. There are already a bunch of vaccines going through this process. Challenge trials is where you purposefully infect subjects. TheY are highlY controversial but according to Oxford, would speed up the research and they are planning to do one.