WSJ : Researchers Infect Volunteers With Coronavirus, Hoping to Conquer Covid-19 Researchers Infect Volunteers With Coronavirus, Hoping to Conquer Covid-19So-called challenge trials have long been used to study infections, but so far only the U.K. is doing them for Covid-19 See attached pdf Download Researchers_Infect_Volunteers_With_Coronavirus__Hoping_to_Conquer_Covid-19_-_WSJ.pdf