The Pandemic Severity Index was produced by the US Department of Health and Human Services (PSI). It was created as a pandemic planning tool by the Centers for Disease Control and Prevention. Because the PSI was developed using a linear method, there were several limits to this clinical scale. In 2014, it was replaced with the Pandemic Severity Assessment System (PSAF), a framework for assessing the severity of a novel influenza pandemic. Let's take a closer look at this pandemic severity assessment tool.