The Nobel Prize in Medicine has been awarded to two scientists whose work led to mRNA vaccines against COVID-19.
As countries prepared to roll out those shots in late 2020, The Associated Press took a look at how the vaccines were developed so quickly.
A head start helped. Over a decade of behind-the-scenes research had new vaccine technology poised for a challenge just as the coronavirus erupted.
Research from the University of Pennsylvania and National Institutes of Health laid the groundwork for unusually rapid development and testing of the shots.
