University of Louisville documenting herd immunity using wastewater and last updated 2021-05-21 11:24:32-04 LOUISVILLE, Ky. â As vaccinations slow down across the country, many experts worry the nation will not reach herd immunity. Thatâs where enough people are immune to a disease to make its spread unlikely. Experts say the more people who get vaccinated, the fewer people the COVID-19 virus can infect, and eventually, the virus will have nowhere to go and the community will be protected. Researchers in Louisville, Kentucky, are tracking herd immunity in a unique way through the Co-Immunity Project. The study, led by the Christina Lee Brown Envirome Institute, the Center for Predictive Medicine and the University of Louisville is testing both wastewater and people and combining the data in hopes of answering the question: how immune is this community to COVID-19?