TCID is widely used in virology for determining viral infectivity. It serves as a quantitative measure to assess the concentration of infectious virus particles in a sample. This application is critical in research and development of vaccines, where precise measurement of viral titers ensures accurate dosing and efficacy testing. TCID is also employed in antiviral drug studies to evaluate the effectiveness of compounds in inhibiting viral replication. Its simplicity and reliability make it a standard method in cell culture-based virological assays.