Many government leaders and citizens are pinning their hopes on the rapid development and deployment of a vaccine against COVID-19. So far, considerable progress has been made toward identifying effective vaccines against COVID-19, and more than 100 candidates are now being evaluated1 . However, successful vaccines typically take years to develop. A vaccine against human immunodeficiency virus has eluded medical science for more than 30 years now, and past attempts to create vaccines against other coronaviruses, such as the agent that causes severe acute respiratory syndrome (SARS), have highlighted the challenging and time-consuming nature of vaccine research and development2–5 . Moreover, the virus that causes COVID-19, SARS-CoV-2, may well mutate; the eventual vaccine may provide only partial protection; and, notably, vaccine hesitancy may preclude large-scale uptake and the development of herd immunity6 . Realistically, the world cannot count on a vaccine breakthrough to decisively end the COVID-19 pandemic any time soon.