We need a vaccine to defend against the Covid 19 pandemic. The news is awash with stories about vaccines that may be ready to go this year, new experimental paradigms for development, and a push to skip a wide range of traditional safety testing measures. Rarely will you hear a vaccinologist or immunologist be pushing these ideas. One of the main reasons is the risk of ADE. Why? The reason is that it can be deadly and far more so than the viral infection itself. It takes well thought out vaccine design, clinical trial protocols, and safety monitoring to insure that truly “the cure is not worse than the disease’. Here are several articles discussing this issue in regards to Covid 19 and a disease with which many travelers and residents of tropical regions will be familiar, Dengue Fever.