TCID is widely used in the field of virology and microbiology for quantifying viral infectivity. It is a critical tool in determining the concentration of infectious virus particles in a sample, often expressed as the 50% tissue culture infectious dose. This method is essential for assessing viral titers during research on viral pathogenesis, vaccine development, and antiviral drug testing. By measuring the dilution of a virus required to infect 50% of cultured cells, TCID provides a reliable and reproducible way to evaluate viral potency and efficacy. It is particularly valuable in studies involving influenza, HIV, and other viruses, enabling researchers to compare viral strains, monitor viral growth, and optimize experimental conditions. Additionally, TCID assays are used in quality control for vaccine production to ensure consistent and effective dosages.