Measles, mumps, and rubella are three contagious viral diseases that can lead to serious health complications. Measles causes a high fever, cough, runny nose, and a distinctive rash. Mumps primarily affects the salivary glands, leading to swelling and pain, while rubella is often milder but can cause serious issues during pregnancy. The MMR vaccine is a combined immunization that protects against all three diseases. It is typically administered to children in two doses, helping to prevent outbreaks and protect public health. Vaccination is crucial for maintaining herd immunity and safeguarding vulnerable populations.