Researchers in Japan said the Omicron variant of COVID-19 is highly transmissible even among vaccinated people or those who have already been infected with other strains of the virus, local media reported Thursday.
At a meeting of an advisory panel to the health ministry on Wednesday, a group led by Kyoto University Professor Hiroshi Nishiura reported the results of their analysis on the rapid spread of the Omicron variant in South Africa.
The group examined genetic information of about 200 cases reported from South Africa from September through the end of November based on an international database.
According to their results, the effective reproduction rate, which represents the average number of people that every person with the virus infects, is 4.2 times higher than that for the Delta variant in Gauteng Province in South Africa where has been hit hard by the Omicron variant.
In addition, the rate is still as more than twice as high even after adjusting the data to account for bias.
The group said the exact transmissibility of the Omicron variant itself remained unclear so far. However, it added that the effectiveness of acquired COVID-19 immunity to protect against the mutant virus stood at only about 20 percent in South Africa.
Professor Nishiura said the Omicron variant could pose a high risk even in countries with high vaccination rates, adding that he would wait for key information including the severity the variant causes and the effectiveness of vaccination.