Abstract: Methods, systems, and apparatus for identifying an adverse event. In one aspect, a method includes obtaining first patient data; applying a machine learning model to the first patient data to identify information indicative of a first adverse event in the first patient data, in which the machine learning model is configured to: identify one or more named entities present in the first patient data; identify information indicative of the first adverse event based on the identified named entities; and output annotated patient data; obtaining feedback data on the annotated patient data, in which the feedback data is usable to refine the machine learning model; applying the refined machine learning model to second patient data to identify information indicative of a second adverse event in the second patient data; and providing information indicative of the second adverse events identified in the second patient data.