"If someone is fully vaccinated against measles (two doses) and has not had a major immunocompromising condition occur (e.g., organ transplant), their immunity should be sufficient with no need for further dosages," says Dr. Amesh A. Adalja, MD, FACP, FACEP, FIDSA, a senior scholar at Johns Hopkins Center for Health Security.

The vaccine is the only way to prevent measles, but it also prevents other illnesses. The other “M” stands for mumps, and the “R” stands for rubella. Children can also get an MMRV vaccine, which adds protection against varicella, better known as chickenpox.