Dr. Sabra Klein has a research program with an overarching goal to uncover the mechanisms that mediate how males and females differ in their immune responses to viral infection and vaccination. They hypothesize that sex chromosome complement and X-linked genes as well as sex steroids and signaling through sex steroid receptors are critical pathways modulating immune responses to viruses. They consider how immunological, hormonal, and genetic differences between males and females affect sex differences in susceptibility to viruses, including influenza, Zika, and SARS-CoV-2 viruses. They also study the mechanisms mediating altered immune responses and infectious disease pathogenesis during pregnancy. Her research indicates that non-pregnant females typically mount more robust immune responses than males, which can be beneficial for the efficacy of vaccines and clearance of viruses, but also can be detrimental by causing immunopathology.