The Ontology of Adverse Eventsy (OAE) is a biomedical ontology in the domain of adverse events. OAE aims to standardize adverse event annotation, integrate various adverse event data, and support computer-assisted reasoning. OAE is a community-based ontology. Its development follows the OBO Foundry principles. Vaccine adverse events have been used as an initial testing use case. OAE also studies adverse events associated with the administration of drug and nutritional products, the operation of surgeries, and the usage of medical devices, etc.