The Omicron coronavirus variant has been reported in 89 countries and the number of cases is doubling in 1.5 to 3 days in areas with community transmission, the World Health Organization (WHO) said on Saturday. Omicron is spreading rapidly in countries with high levels of population immunity, but it is unclear if this is due to the virus ability to evade immunity, its inherent increased transmissibility or a combination of both, the WHO said in an update. The agency designated Omicron a variant of concern on Nov. 26, soon after it was first detected, and much is still not known about it, including the severity of the illness it causes. "There are still limited data on the clinical severity of Omicron," the WHO said. "More data are needed to understand the severity profile and how severity is impacted by vaccination and pre-existing immunity." It added, "There are still limited available data, and no peer-reviewed evidence, on vaccine efficacy or effectiveness to date for Omicron". Paris has cancelled planned fireworks as well as festivities on the Champs Elysees avenue on New Years Eve in line with new government rules to prevent the spread of Omicron, BFM TV reported on Saturday. French Prime Minister Jean Castex said on Friday major public parties and fireworks would be banned on New Years Eve and recommended that people - even if vaccinated - take a COVID-19 self-test before getting together for year-end parties. Omicron is now suspected to be responsible for up to 10% of new confirmed COVID-19 cases in France and is the main reason behind plans for stricter health requirements for entering some venues, the health minister said on Saturday.