U.S. COVID-19 vaccine distribution strategies, systems, performance, and lessons learned, December 2020 - May 2023

During December 2020 through May 2023, the Centers for Disease Control and Prevention's (CDC) Immunization Services Division supported and executed the largest vaccine distribution effort in U.S. history, delivering nearly one billion doses of COVID-19 vaccine to vaccine providers in all 50 states, District of Columbia, Puerto Rico, Virgin Islands, Guam, Federated States of Micronesia, American Samoa, Marshall Islands, Northern Mariana Islands, and Palau. While existing infrastructure, ordering, and distribution mechanisms were in place from the Vaccines for Children Program (VFC) and experience had been gained during the 2009 H1N1 pandemic and incorporated into influenza vaccination pandemic planning, the scale and complexity of the national mobilization against a novel coronavirus resulted in many previously unforeseen challenges, particularly related to transporting and storing the majority of the U.S. COVID-19 vaccine at frozen and ultra-cold temperatures. This article describes the infrastructure supporting the distribution of U.S. government-purchased COVID-19 vaccines that was in place pre-pandemic, and the infrastructure, processes, and communications efforts developed to support the heightened demands of the COVID-19 vaccination program, and describes lessons learned.