Vaccine adverse event

A vaccine adverse event (VAE), sometimes referred to as a vaccine injury, is an adverse event believed to have been caused by vaccination. The World Health Organization (WHO) knows VAEs as Adverse Events Following Immunization (AEFI).

AEFIs can be related to the vaccine itself (product or quality defects), to the vaccination process (administration error or stress related reactions) or can occur independently from vaccination (coincidental).

Most vaccine adverse events are mild. Serious injuries and deaths caused by vaccines are very rare, and the idea that severe events are common has been classed as a "common misconception about immunization" by the WHO. Some claimed vaccine injuries are not, in fact, caused by vaccines; for example, there is a subculture of advocates who attribute their children's autism to vaccine injury, despite the fact that vaccines do not cause autism.

Claims of vaccine injuries appeared in litigation in the United States in the latter part of the 20th century. Some families have won substantial awards from sympathetic juries, even though many public health officials have said that the claims of injuries are unfounded. In response, several vaccine makers stopped production, threatening public health, resulting in laws being passed at several points to shield makers from liabilities stemming from vaccine injury claims.