We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions.
Keywords: Alpha variant; COVID-19; Delta variant; SARS-CoV-2; Vietnam; coronavirus disease; coronaviruses; outbreak; respiratory infections; severe acute respiratory syndrome coronavirus-2; spatiotemporal evolution; viruses; zoonoses.