Diarrhea as an adverse event following immunization [AEFI]

Wed, 18 Mar 2026 08:11:16 +0000

Authors: Brighton Collaboration

Location: United States

Purpose #

Diarrhea is a common medical condition characterized by increased frequency of bowel movements and increased liquidity of stool. Although acute diarrhea is typically self-limiting, it can be severe and can lead to profound dehydration, which can result in abnormally low blood volume, low blood pressure, and damage to various organs. Acute diarrhea remains a major cause of infant mortality globally, with over 2 million deaths attributed to it each year, mostly in the developing world. Children and the elderly are particularly prone to dehydration secondary to diarrhea. Diarrhea is also a commonly reported AEFI in both passive surveillance systems and clinical trials, for both oral and non-oral vaccines. The lack of a commonly accepted, standardized definition for diarrhea as an AEFI hinders comparability and uniform reporting across various study settings or surveillance systems.

Dehydration on Open Syndrome Initiative

Diarrhea as an adverse event following immunization [AEFI]

Purpose #