Serology is a branch of medical science that focuses on the study of blood serum, which is the clear liquid that remains after blood clots. It is primarily used to detect and measure the presence of antibodies, proteins produced by the immune system in response to infections or vaccinations. By analyzing serum samples, healthcare professionals can diagnose various diseases, including HIV, hepatitis, and COVID-19. In addition to diagnosing infections, serology can also help determine immunity to certain diseases. For example, testing for antibodies against measles or chickenpox can indicate whether a person has been vaccinated or previously infected. This information is crucial for public health efforts and individual health management.