> The aim of the study was to identify the lowest amount of virus to safely and reliably infect someone, so researchers can later easily test the efficacy of vaccines or antivirals on future challenge trial volunteers. “Of course, in doing that, you learn a lot about the actual disease, which indeed we have,” said Dr. Andrew Catchpole, chief scientific officer at hVIVO, a British clinical and laboratory services company that partnered with Imperial College London to conduct Britain’s Covid-19 challenge study.