Diarrhea after vaccination may be caused by vaccine adverse reaction, enteritis, diet and other reasons. 1. Adverse vaccine reaction: it may be caused by the body’s immune response, and it is very likely that there will be adverse reactions after vaccination, such as diarrhea, nausea, vomiting, abdominal pain and other symptoms. 2. Enteritis: enteritis may be caused by infection, immune damage and other reasons. It may be caused by the patient’s own intestinal inflammation, after the vaccine because the body’s immune ability may be reduced, after the attack of intestinal inflammation, the diarrhea appeared. 3. Improper diet: It may also be caused by eating too cold or too spicy food before vaccination, which may stimulate the intestinal tract and lead to diarrhea. Diarrhea after vaccination may also be caused by other reasons, it is recommended that patients with diarrhea after vaccination go to the hospital in a timely manner, in accordance with the doctor’s instructions for the use of medication and treatment, to avoid delays in the condition.