A baby’s fever after the MMR vaccine will get better in about 3 to 5 days. MMR belongs to the triple vaccine, which can be used to protect against three viral infections such as rubella, measles and mumps. Some babies will have low-grade fever after entering the vaccine, which is considered to be related to the vaccination reaction. It is recommended that babies should be kept in the hospital for half an hour for observation after vaccination. If the fever after vaccination does not exceed 38.5 degrees, you can choose to take more rest, hydrate and promote metabolism to relieve it. If the fever exceeds 38.5 degrees, you need to give ibuprofen, acetaminophen and other drugs to reduce fever treatment, most babies in 3~5 days, fever symptoms can be improved. Be alert to the combination of bacterial and viral infections, if the fever is severe or persistent, be sure to go to the hospital in time.