The Omicron variant of the novel coronavirus reduces vaccine efficacy and is more transmissible than the Delta strain but causes less severe symptoms according to early data, the World Health Organization said on Sunday.
It also stated that current available data suggests that it is likely that Omicron will outpace the Delta variant where community transmission occurs.
It, however, stressed that lack of data meant it could not say if Omicron's rate of transmission was because it was less prone to immune responses, higher transmissibility or a combination of both.
Omicron infections have so far caused "mild" illness or asymptomatic cases, but the WHO said the data was insufficient to establish the variant's clinical severity.