The World Health Organization on Sunday said that the Omicron coronavirus variant is more transmissible than the Delta strain and reduces vaccine efficacy but causes less severe symptoms according to early data.
According to AFP report, the Delta variant, first identified in India earlier this year, is responsible for most of the world's coronavirus infections.
The WHO said Omicron had spread to 63 countries as of December 9. Faster transmission was noted in South Africa, where Delta is less prevalent, and in Britain, where Delta is the dominant strain.
But it stressed that a 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.
"Given the current available data, it is likely that Omicron will outpace the Delta variant where community transmission occurs," it added.
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.
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On November 24, South Africa reported Omicron to the global health body.
Vaccine manufacturers Pfizer/BioNTech last week said three doses of their vaccines were still effective against Omicron.
Meanwhile, Kerala, Andhra Pradesh and Chandigarh reported their first Omicron case on Sunday, while Maharashtra and Karnataka each recorded one more case of the COVID-19 variant, taking the tally in India to 38. The Omicron variant was first detected in India in Bengaluru with two people testing positive for it comprising a South African national of Indian origin and a doctor.
Cases of Omicron, which is categorised as a "variant of concern" by the World Health Organisation, have been detected in about 60 countries.