Researchers at the University of Oxford are preparing a “challenge trial” to test how individuals previously infected with and recovered from COVID-19 respond to being reinfected. Challenge trials are an ethically controversial practice where participants are intentionally exposed to a disease. The trial will involve healthy 18-30 year olds and be conducted in a specialized hospital site where they will be isolated for 17 days after exposure to the virus. The aim of the trial is to determine how the body responds to prior infection and better tailor future treatments and vaccines.