MMR generally refers to MMR vaccine, there is no limit to how many days you can go out with MMR vaccine, it is commonly 1~3 days. Adverse reactions to MMR vaccine are serious and require prompt medical attention. After the injection of MMR vaccine, observe your body to see if there is any reaction to the vaccination, if there is no adverse reaction to the vaccine within 1~3 days or the adverse reaction to the vaccine is relatively mild, you can go out, and you have to do a good job of protection when you go out. If there are adverse reactions such as fever, headache and allergic rash after MMR vaccination, you can stay at home for a while and rest for a period of time. Going out may be attacked by other viruses and aggravate the adverse reactions to the vaccine. If the adverse reaction persists for a long time after receiving the MMR vaccine, or even if the symptoms worsen, you can go to the hospital in time.