The Measles, Mumps, Rubella (MMR) test assesses immunity to these viral infections. Clinical use involves confirming vaccination status or past infections. Symptoms vary for each disease; measles presents with fever and a characteristic rash, mumps with swelling of salivary glands, and rubella with a rash and mild fever. The MMR test is vital for public health, ensuring adequate immunity levels and guiding vaccination strategies. Early identification of susceptibility helps prevent outbreaks and serious complications associated with these infections.