Intrusive memories of a traumatic event are distressing, vivid mental images that spring to mind unbidden, and the core clinical symptom in PTSD (Posttraumatic Stress Disorder) and ASD (Acute Stress Disorder). We propose that a brief science-derived intervention can be delivered in the first few hours after a traumatic event as a so-called “cognitive therapeutic vaccine” to prevent the recurrence of intrusive memories of trauma. Our approach differs from traditional talking therapies in various ways including: a) focusing on one core clinical symptom as a treatment target, rather than a whole disorder; b) deriving a novel type of intervention technique informed by neuroscientific insights and experimental research, rather than adapting existing psychotherapy techniques; c) aiming for scalability from the onset, rather than an adaptation of face-to face therapy. The behavioural intervention technique was developed in the laboratory with a focus on perceptual intrusive memory. It uses cognitive task interference as a hypothesised blockade of sensory mental imagery during trauma memory consolidation to reduce the frequency of intrusive memories of trauma. In early tests of clinical translation from the laboratory to real-world single event trauma, the technique has involved a 25-minute, single-session procedure (including Tetris computer game play), delivered in a hospital within 6 hours of a traumatic event. Results of two proof-of-concept trials provide initial support for the efficacy of the intervention: there were fewer intrusive memories compared to control when delivered in hospital within 6 hours following both traumatic motor vehicle accidents (Iyadurai et al., 2018) and traumatic childbirth (Horsch et al., 2017). Both studies indicated that the intervention was met with acceptability. Future trials are warranted as well as mechanistic research with cultural adaptability in mind.