In mid-November, South African scientists (which have a robust genetic-sequencing capability) discovered a new coronavirus variant, which the WHO subsequently named Omicron. The WHO has labeled Omicron a “variant of concern,” joining previous strains.
To be labeled a “variant of concern,” a variant must satisfy one or more of the following three diagnostic criteria: essentially, it must be more transmissible, more severe (or different in symptoms), or less effective than previously available vaccines and medicines.