Categories of Causality Conclusions*

Contents

To summarize the evidence regarding potential adverse events in an accurate, concise, practical and standardized manner, we established the categories of causality conclusions. These categories are used throughout the site.

CategoriesDefinitions
Vaccines can cause the event.The evidence shows a clear association between the event and at least one vaccine routinely recommended in the U.S.
Vaccines did cause the event.The evidence showed a clear association between the event and at least one previously recommended vaccine. However, these vaccine(s) are no longer used in the U.S., if they ever were.
Vaccines have not been shown to cause the event.The evidence of an association between the event and vaccines currently routinely recommended to the general population in the United States is insufficient or non-existent.
Vaccines do not cause the event.The evidence shows clear lack of association between the event and vaccines currently routinely recommended to the general population in the United States.
* These conclusions do not necessarily consider vaccines recommended only for special populations in the United States such as Yellow Fever vaccine (international travelers) or Smallpox vaccine (military personnel).