The consortium formed to run Britain’s Covid challenge trial, which included scientists who trained at the Common Cold Unit, had access to the British National Health Service’s robust, real-time data on Covid hospitalizations and deaths. The researchers designing the study said they felt confident that there was little risk to the healthy unvaccinated 18-to-30-year-old volunteers they recruited for the trial. There were no severe adverse events in the 36 people who participated, and they will continue to be monitored over the next year.

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.

The volunteers were infected with the original SARS-CoV-2 strain first discovered in Wuhan, China. A Delta strain is being developed to be used in possible later challenge trials. “Coronaviruses are not going away and there is going to be continual risk of new highly pathogenic coronaviruses coming along,” said Dr. Chiu. “We need to understand those immune factors much better so we are better prepared for the next pandemic when it comes.”