There is no relationship between the MMR vaccine and toddler rash. Measles is caused by human herpesvirus type 6 and 7 infection, and is a common acute febrile rash disease in infants and young children, and there is no obvious relationship with the MMR vaccination. Children with measles usually develop fever first, and the temperature will drop to normal after 3-5 days of fever, followed by the appearance of rash, which is a red maculopapular rash. The red papular rash after MMR vaccination is considered to be caused by the adverse reaction of the vaccine, and attention should be paid to keep the skin of the child clean, and observe whether there are other adverse reactions in the child, and if the situation is serious, the child should be brought to the hospital for consultation, and be treated as soon as possible under the guidance of the doctor, to avoid further aggravation of the condition.