Whether T cells join the immune system's fight against SARS-CoV-2, the virus that causes COVID-19, has been unclear. Two new studies have identified T cells that react to the virus in patients who had COVID-19 or were recovering from it. Both studies detected helper T cells, which orchestrate antiviral responses of other immune cells, and one of the studies also found killer T cells that eliminate virally infected cells. Both studies also discovered helper T cells that target the virus in blood samples from people who had never been infected. These people likely had the cells because they had been infected by similar coronaviruses that cause colds. The results suggest the virus induces a strong T cell response in patients, but they do not indicate whether people who have recovered from COVID-19 are immune to the virus.