Children who have been vaccinated with MMR vaccine may develop a fever within 12 days after vaccination, but some children may not develop a fever. MMR vaccine is a vaccine that can be used to prevent three diseases: mumps, rubella and measles, and is usually given at 8 months of age or older. Adverse reactions such as mild fever, rash and swollen lymph nodes may occur after vaccination, mostly within 12 days of vaccination. However, some children have no adverse reactions after vaccination. Fever after MMR vaccination is usually mild, mostly low-grade and transient, and can be relieved on its own. If the temperature exceeds 38.5 degrees, ibuprofen, acetaminophen and other medicines can be taken as prescribed by the doctor to reduce heat treatment. If a child who has received MMR vaccine has recurrent fever, or high fever that does not go away, it may be combined with other diseases, and it is necessary to consult a doctor to clarify the cause of the disease and give targeted treatment.