The newly discovered Omicron COVID-19 variant likely spreads faster than the Delta variant, the World Health Organization (WHO) noted in a technical brief, adding that vaccines may be less effective against it.
"(Omicron) is spreading faster than the Delta variant in South Africa where Delta circulation was low, but also appears to spread more quickly than the Delta variant in other countries where the incidence of Delta is high, such as in the United Kingdom," the WHO said, citing preliminary evidence.
It added that there was some suggestion, particularly due to changes to the spike protein, that vaccines would be less effective against the variant.
Research released on Friday by the UK Health Security Agency found that a full two-dose vaccination course was less effective against symptomatic disease with Omicron than with the original strain of COVID-19 or the Delta variant.
It found however that "moderate to high vaccine effectiveness against mild infection of 70-75% was seen in the early period after a booster dose."
But, the WHO said there was still very limited data on vaccine effectiveness for Omicron and how severe the new variant is.
While South African researchers have said that there is some indication that Omicron is less severe than the Delta variant and most cases in the EU are mild, "it remains unclear to what extent Omicron may be inherently less virulent," the technical note said.
UK researchers warned on Saturday that further measures should be taken to prevent transmission, stating that Omicron could quickly become the dominant strain of COVID-19 in the country and cause tens of thousands of additional deaths by the spring.
Omicron was first identified as a variant of concern in late November and has since been identified in 63 countries.