Can a 5-year-old with leukemia currently receiving chemotherapy get the MMR vaccine?

A 5-year-old with leukemia who is currently undergoing chemotherapy should not receive the MMR (measles, mumps, and rubella) vaccine because it is a live attenuated vaccine. Live vaccines contain a weakened form of the virus that can still replicate in the body to provoke an immune response. In patients receiving chemotherapy, especially for conditions like leukemia, the immune system is often compromised. This immunosuppression puts them at a higher risk for experiencing adverse effects from live vaccines, including the possibility of developing the disease the vaccine is intended to prevent.

Healthcare guidelines generally recommend that live vaccines, such as MMR, be avoided in individuals who are moderately to severely immunocompromised due to treatment such as chemotherapy. Non-live vaccines are typically safer options for these individuals, as they do not contain live organisms that could pose a risk to an already weakened immune system.