"As of 9 December 2021, cases of human infections with this variant have been identified in 63 countries across all six WHO regions," the overview by the WHO read.

It is not clear yet, why the new strain is spreading so fast, the organization added.

"However, given the current available data, it is likely that Omicron will outpace the Delta variant where community transmission occurs," the document said.

The Omicron variant might reduce the effectiveness of COVID-19 vaccines based on preliminary data, but this strain is less dangerous than Delta, the organization assumed.

"There are limited available data, and no peer-reviewed evidence, on vaccine efficacy or effectiveness to date for Omicron. Preliminary evidence, and the considerably altered antigenic profile of the Omicron spike protein, suggests a reduction in vaccine efficacy against infection and transmission associated with Omicron," the statement said.