The MMRV vaccine, also known as the Measles, Mumps, Rubella, and Varicella vaccine, is a crucial immunization that protects young children against these illnesses. There are several synonyms for the MMRV vaccine that healthcare providers and parents may use, including the "4-in-1 vaccine" or the "3-in-1 plus chickenpox vaccine." The MMRV vaccine is given in two doses with the first dose administered between 12-15 months old and the second dose between 4-6 years old. It is highly effective in preventing the spread of these diseases and can help to protect children from serious complications such as deafness, blindness, and even death.