PROJECT SUMMARY Candidate. Kimberly G. Blumenthal, MD, MSc is an allergist/immunologist at Massachusetts General Hospital (MGH) and an Assistant Professor of Medicine at Harvard Medical School. After studying economics at Columbia University, she received her MD from Yale University. Dr. Blumenthal completed Internal Medicine and Allergy/Immunology training at MGH, and a Masters of Science at the Harvard T.H. Chan School of Public Health. Dr. Blumenthal aims to be an international leader in drug allergy epidemiology and simulation research. Mentorship, Training Activities, and Environment. Dr. Blumenthal was mentored by Rochelle P. Walensky, MD, MPH until her departure in January 2021 to direct the Centers for Disease Control and Prevention. Dr. Walensky was NIH-funded from 2006-2021; she had successfully transitioned >5 fellows to independent R01- funded research careers. Dr. Blumenthal’s current mentor is Dr. Carlos Camargo, an internationally recognized expert in anaphylaxis and NIH-funded epidemiologist. Dr. Blumenthal has acquired new skills, including linkage and analysis of large databases, resource utilization analysis, and simulation modeling and cost-effectiveness analysis. The collaborative opportunities, intellectual environment, and resources available to Dr. Blumenthal are outstanding and provide her with a clear path to independence. Research. Penicillin (PCN) allergy is reported by over 10% of the U.S. population, though a self-reported PCN allergy infrequently reflects an inability to tolerate PCNs and other beta-lactam antibiotics. Unnecessary use of beta- lactam alternative antibiotics leads to more antimicrobial resistance and healthcare-associated infections. Beta-lactam antibiotics are the most common cause of drug hypersensitivity reactions, the immune-mediated subset of adverse drug reactions. PCN allergy evaluation can distinguish between patients with and without true PCN hypersensitivity. The K01 scientific program, The Clinical and Economic Impact of Penicillin Allergy, has three specific aims that align with national priorities including curbing antimicrobial resistance: 1) To assess the clinical and economic impact of reported PCN allergy. 2) To determine the frequency, predictors, and healthcare resource impact of beta-lactam antibiotics. 3) To project the clinical outcomes, budgetary impact, and cost-effectiveness of PCN allergy evaluation. Completion of this research proposal and training plan will position Dr. Blumenthal for an independent research career as a drug allergy expert with methods skills in clinical epidemiology and decision science.