LONDON : Much of the world spent the past year taking vaccines and wearing masks to evade Covid-19. In the U.K., almost four dozen volunteers have had the virus dripped into their noses by syringe in clinical experiments.
So-called human challenge studies—which intentionally expose healthy people to viruses and other pathogens to study illness, vaccines and treatments—aren’t new.
Scientists globally have used them for decades to assess how infections and drugs behave from the moment they enter the body.
But only the U.K. has pushed ahead with Covid-19 challenge trials, deliberately infecting volunteers to study a new, sometimes-deadly disease that still harbors many unknowns.