This directed case study introduces the basics of blood typing and discusses possible correlations for contracting COVID-19 by blood type. After students complete a set of activities designed to help them understand how blood type is determined at the cellular level, they then consider preliminary data collected from hospitals in China during the early months of the COVID-19 outbreak. Students are asked to examine the findings of a preprint manuscript using basic statistics to evaluate the authors’ conclusions. Through the process of critical examination and the application of basic quantitative skills, students evaluate the preprint as though they were reviewers. The case concludes with a question set that ties together blood type, antibodies, and risk of contracting COVID-19. It would be helpful for students to have a basic understanding of immunology before they start the case, although it is not required. Designed for college-level anatomy and physiology students, the case could be used when covering the cardiovascular system, the components of blood, and the production of blood cells.