On Nov. 24, 2021, the variant B.1.1.529 was first identified in South Africa, and only two days later, WHO announced that B.1.1.529 constitutes a variant of concern, named “Omicron”. There are more than 30 mutation sites on the S gene of variant B.1.1.529. Omicron has a greater binding affinity than the original SARS-CoV-2 virus, with levels more comparable to what we see with the Delta variant. Some of the mutations have been detected in previous variants, such as Alpha and Delta, and have been associated with increased transmissibility and immune evasion. Many of the other identified mutations are not yet well characterized and have not been identified in other currently circulating variants. More investigations are underway to determine the possible impact of these mutations. Omicron includes Pango lineage B.1.1.529 and descendent Pango lineages BA.1, BA.1.1, BA.2 and BA.3.