Genomic Surveillance for SARS-CoV-2 Variants Circulating in the United States, December 2020-May 2021. - Paul, Prabasaj; France, Anne Marie; Aoki, Yutaka; Batra, Dhwani; Biggerstaff, Matthew; Dugan, Vivien; Galloway, Summer; Hall, Aron J.; Johansson, Michael A.; Kondor, Rebecca J.; Halpin, Alison Laufer; Lee, Brian; et al. (MMWR: Morbidity & Mortality Weekly Report, 2021)