But cellular immune responses are longer lasting — and as Jennifer Gommerman, an immunologist at the University of Toronto in Canada, explains: “Cellular immunity is what’s going to protect you from disease.” Memory B cells, which can rapidly deploy more antibodies in the event of re-exposure to the virus, tend to stick around, and so do T cells, which can attack already-infected cells. Both provide an added measure of protection should SARS-CoV-2 sneak past the body’s first line of defence.