As COVID-19 is new to humankind and the nature of protective immune responses is poorly understood, it is unclear which vaccine strategies will be most successful. Therefore, it is imperative to develop various vaccine platforms and strategies in parallel. Indeed, since the outbreak began, researchers around the world have been racing to develop COVID-19 vaccines, with at least 166 vaccine candidates currently in preclinical and clinical development. To meet the urgent need for a vaccine, a new pandemic vaccine development paradigm has been proposed that compresses the development timeline from 10–15 years to 1–2 years 6. However, there remains a lack of clarity as to what may constitute a safe and immunologically effective COVID-19 vaccine strategy, how to define successful end points in vaccine efficacy testing and what to expect from the global vaccine effort over the next few years. This Review outlines the guiding immunological principles for the design of COVID-19 vaccine strategies and analyses the current COVID-19 vaccine landscape and the challenges ahead.