Need another reason to get vaccinated? It prevents sepsis, the condition that makes COVID-19 deadly Marie McCullough, The Philadelphia Inquirer April 28, 2021 FacebookTwitterEmail Increase your arm’s blood flow post-vaccine and swing it around.FotoDuets/Getty Images/iStockphoto PHILADELPHIA — The reason severe COVID-19 is so deadly is that it unleashes a condition called sepsis. Sepsis occurs when an abnormal immune response to an infection damages the body’s own tissues, leading to organ failure. Of the 26,266 people who were hospitalized with COVID-19 in Pennsylvania in the first seven months of the pandemic, about 8,000, or 31%, also were diagnosed with sepsis, according to a new report from the Pennsylvania Health Care Cost Containment Council (PHC4).