A vaccine, like any medicine, is capable of causing serious problems, such as severe allergic reactions. The risk of MMR vaccine causing serious harm, or death, is extremely small.

Getting MMR vaccine is much safer than getting any of these three diseases.

Most people who get MMR vaccine do not have any problems with it.

Mild Problems

• Fever (up to 1 person out of 6)
  
• Mild rash (about 1 person out of 20)
  
• Swelling of glands in the cheeks or neck (rare)
  

If these problems occur, it is usually within 7-12 days after the shot. They occur less often after the second dose.

Moderate Problems

• Seizure (jerking or staring) caused by fever (about 1 out of 3,000 doses)
  
• Temporary pain and stiffness in the joints, mostly in teenage or adult women (up to 1 out of 4)
  
• Temporary low platelet count, which can cause a bleeding disorder (about 1 out of 30,000 doses)
  

Severe Problems (Very Rare)

• Serious allergic reaction (less than 1 out of a million doses)
  
• Several other severe problems have been known to occur after a child gets MMR vaccine. But this happens so rarely, experts cannot be sure whether they are caused by the vaccine or not. These include:
  
  • Deafness
    
  • Long-term seizures, coma, or lowered consciousness
    
  • Permanent brain damage