The World Health Organization said Sunday in a technical brief that although the Omicron coronavirus variant has less severe symptoms than the Delta variant, it is more transmissible and reduces vaccine efficacy.

While the Delta variant is responsible for most of the world's coronavirus infections, South Africa's discovery of Omicron -which has a large number of mutations- last month urged countries around the world to impose travel bans on southern African countries and reinstate local restrictions to slow its spread.

The WHO said that as of December 9, Omicron has spread to 63 countries. A faster transmission was noted in South Africa, where Delta is less dominant, and in Britain, where Delta is the prevailing variant.

On another note, the WHO stressed that due to the lack of data, it could not say whether Omicron's transmission rate was the result of being less prone to immune responses, higher transmissibility, or a combination of both.

The WHO added in the brief “Early evidence suggests Omicron causes a reduction in vaccine efficacy against infection and transmission.”

“Given the current available data, it is likely that Omicron will outpace the Delta variant where community transmission occurs.”

The WHO’s statement comes today following statements by vaccine manufacturers Pfizer/BioNTech last week saying three doses of their jabs were still effective against the Omicron variant.