How T cells can protect unexposed people from COVID-19

Professor Stephen Turner, Head of Department of Microbiology, Co-Head Infection and Immunity Program, Co-Head Monash BDI’s COVID-19 Program

The Age, The Sydney Morning Herald and stuff reported on emerging evidence that between 20 and 50 per cent of people who have never been exposed to COVID-19 have immune cells that can recognise and react to the virus. Scientists suspect that some people who have been exposed to other sorts of viruses develop T cells that can also target SARS-CoV-2. The BDI’s  Professor Stephen Turner was quoted in the story as saying that in the best-case scenario, cross-reactive T cells do offer some protection. “That's why we might be seeing so much asymptomatic infection. If there is a level of protection, due to previous exposure, you have less symptoms – because you're limiting the amount of virus that can grow,” he said. Professor Turner said T cells needed the right signals to be activated.