That makes it difficult to know if vaccine developers are really on the right track. Their hunch is based, primarily, on how the immune system responds to other pathogens. But some viruses evade the typical patterns. They short-circuit the immune response. The most infamous example of that is HIV, Wherry says, which attacks the very T cells that would coordinate the immune response to the virus. SARS-CoV-2 has already offered its own twists and turns, like its propensity to prompt runaway immune responses. For Covid-19, “there’s no prototypical immune response, especially in severe cases,” Wherry says.
Lately, though, systematic studies of T and B cell responses to SARS-CoV-2 have begun to elicit some patterns. Recently, researchers at the La Jolla Institute for Immunology looked at T cell responses in what they considered “average” cases of the disease—people who got sick but didn’t need to be hospitalized. In a study