For decades, immunobiologists have pondered what are the long-term effects of infections on people’s immune systems. For instance, after the organism fights off a pathogen, does the immune system return to a previous baseline, or could a single infection change it in ways that alter how it will respond not only to an already familiar virus or bacteria but also to a new pathogenic threat? Now, a team of researchers led by Yale University and the National Institute of Allergy and Infectious Diseases (NIAID) has systematically analyzed...