FILE - In this Friday, Jan. 22, 2021 file photo, empty vials of the Pfizer-BioNTech COVID-19 vaccine are seen at a vaccination center at the University of Nevada, Las Vegas in Las Vegas. Makers of COVID-19 vaccines need everything to go right as they scale up from early-stage production to hundreds of millions of doses – and any little hiccup could cause a delay. (AP Photo/John Locher)
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