FormalPara Galit Alter

is at Harvard Medical School and the Ragon Institute, Boston, MA, USA.

FormalPara Kate Bingham

is at SV Health Managers, London, UK, and chairs the UK Vaccines Taskforce.

FormalPara Larry Corey

is at the Fred Hutchinson Cancer Research Center, Seattle, WA, USA.

FormalPara James Dahlman

is at Georgia Institute of Technology and Emory University, Atlanta, GA, USA.

FormalPara Nick Jackson

is at Coalition for Epidemic Preparedness Innovations, Shanghai, China.

FormalPara John Moore

is at Weill Cornell Medical School, New York, NY, USA.

FormalPara Rino Rappuoli

is at GlaxoSmithKline, Siena, Italy.

Questions swirl around trailblazing COVID-19 vaccines as they enter late-stage clinical testing (Tables 1 and 2), with anticipation building for an Emergency Use Authorization in the United States. How is broadening knowledge of immune responses to SARS-CoV-2 informing vaccine research? What are the pros and cons of the different vaccine modalities in discovery and clinical development? What are the key challenges associated with clinical testing, and what are their implications for safety and efficacy of immunization programs in the broader global population? And what issues related to regulatory oversight, manufacturing and distribution are likely to be important in the rollout of a COVID-19 vaccine?