How could scientists race out COVID-19 vaccines so fast without cutting corners?
A head start helped -- over a decade of behind-the-scenes research that had new vaccine technology poised for a challenge just as the coronavirus erupted.
Both shots -- one made by Pfizer and BioNTech, the other by Moderna and the National Institutes of Health -- are so-called messenger RNA, or mRNA, vaccines, a brand-new technology.
U.S. regulators are set to decide this month whether to allow emergency use, paving the way for rationed shots that will start with health workers and nursing home residents.
Traditionally, making vaccines required growing viruses or pieces of viruses — often in giant vats of cells or, like most flu shots, in chicken eggs — and then purifying them before next steps in brewing shots.