Not all adverse events can be prevented given the knowledge, information and the state of the art of medical care at the time of the incident. For example, an allergic reaction to a drug administered for the first time is an adverse event but would be considered unpreventable given the lack of pre-existing knowledge of the patient’s idiosyncratic allergy. However, any subsequent administration of this drug to this patient would be - under most circumstances - considered a preventable medication error, and constitute a clear safety failure. It is incumbent on providers to ensure this information is recorded, and verified with the patient or their surrogates prior to administration. For example, the incidence of some types of healthcare-associated infections, previously considered unpreventable, has been reduced and even eradicated (Berenholtz et al 2011, Pronovost et al 2006). In the previous drug reaction example, preventabilitv may improve through precision medicine - the ability to predict the likely outcome of administering a medication based on the patient’s unique genetic or biological characteristics.