A preventive approach to Post-Traumatic Stress Disorder (PTSD) through an Immediate Psycho-Trauma Intervention (IPTI) may significantly reduce PTSD likelihood and provide a cost-effective way to alleviate suffering. This mixed-method study 1) compared medics who received an IPTI to those who did not after a mass medical event, 2) compared the number medics diagnosed with PTSD from the IPTI group to the minimum number in similar cases reported in the literature. The results indicated that 1.09 % of the medics who underwent the IPTI (N = 275) followed by peer discussion groups and a memorial ceremony were formally diagnosed with PTSD in contrast to the 5 %-20 % reported in similar circumstances. Of these, all but three resumed work within their emergency medical teams. In the one-year qualitative follow-up interviews (N = 14), the IPTI recipients exhibited significantly fewer PTSD symptoms and negative effects than the non-IPTI group. They reported fewer negative themes and a reduced need for professional psycho-trauma assistance, with no significant differences in event recollections between groups. These findings point to the efficacy of the VIOS IPTI in mitigating PTSD risk and suggest its potential for widespread application in clinical settings as a preemptive measure in response to traumatic events.