The MITIGATE study aims to evaluate the real-world clinical effectiveness of pre-treatment with icosapent ethyl (IPE), compared with usual care, on laboratory-confirmed viral upper respiratory infection (URI)-related morbidity and mortality in adults with established atherosclerotic cardiovascular disease (ASCVD). IPE is a highly purified and stable omega-3 fatty acid prescription medication that is approved for cardiovascular risk reduction in high-risk adults on statin therapy with elevated triglycerides. Preclinical data and clinical observations suggest that IPE may have pleiotropic effects including antiviral and anti-inflammatory properties that may prevent or reduce the downstream sequelae and cardiopulmonary consequences of viral URIs. MITIGATE is a virtual, electronic health record-based, open-label, randomized, pragmatic clinical trial enrolling ∼16,500 participants within Kaiser Permanente Northern California – a fully integrated and learning health care delivery system with 21 hospitals and >255 ambulatory clinics serving ∼4.5 million members. Adults ≥50 years with established ASCVD and no prior history of coronavirus disease 2019 (COVID-19) will be prospectively identified and pre-randomized in a 1:10 allocation ratio (∼ 1,500 IPE: ∼15,000 usual care) stratified by age and previous respiratory health status to the intervention (IPE 2 grams by mouth twice daily with meals) vs the control group (usual care) for a minimum follow-up duration of 6 months. The co-primary endpoints are moderate-to-severe laboratory-confirmed viral URI and worst clinical status due to a viral URI at any point in time. The MITIGATE study will inform clinical practice by providing evidence on the real-world clinical effectiveness of pretreatment with IPE to prevent and/or reduce the sequelae of laboratory-confirmed viral URIs in a high-risk cohort of patients with established ASCVD.