MMR generally refers to the MMR vaccine. Fever after one week of MMR vaccination is mainly due to the adverse reaction of the vaccine, which usually resolves on its own and is not a cause for concern. The MMR vaccine is a live attenuated vaccine that stimulates an immune response in the vaccinated person. Some people may experience mild fever one week after receiving MMR vaccine, accompanied by localized lymph node swelling, skin rash and other symptoms, which are not contagious and can be relieved with time, so there is no need to worry too much. MMR vaccination can prevent measles, mumps and rubella, three acute respiratory infections, but it is not 100% possible to avoid these diseases after vaccination. In your daily life, you should also take precautions to avoid close contact with other people and go to less crowded environments to minimize your chances of getting infected. Patients who have fever after one week of MMR vaccination should go to a regular hospital to find out the cause of the disease if the fever is not relieved for a long time and the fever is getting worse.