Evaluating COVID-19 vaccine Histories using OpenSAFELY (ECHO) is funded by the Research for Patient Benefit programme at the National Institute for Health and Care Research, and involves collaborators from the University of Oxford, London School of Hygiene and Tropical Medicine, and University of Bath. We’ll use the OpenSAFELY platform to comprehensively describe COVID-19 vaccine histories, across the whole of England, from the start of the vaccination programme onwards. This includes vaccine timings, the intervals between successive vaccines, and the types and combinations of vaccines received in different groups of people.