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The omicron variant of the coronavirus is more likely than the delta variant to escape the protection built by vaccines or a previous infection, Japanese scientists have reported.

A team of researchers headed by Hiroshi Nishiura, a Kyoto University professor, also told the health ministry’s advisory board Wednesday that omicron’s effective reproduction number, or the average number of people who contract the variant from one infected person, was significantly higher than that of the delta variant.

Its findings were reportedly based on an analysis of data amounting to about 200 cases confirmed in South Africa, where the omicron variant was first detected, from late September to November.

In the South African province of Gauteng, considered the epicenter of the new variant, its effective reproduction number was at least twice as high and even up to 4.2 times higher, the team said.

Nishiura’s team noted that the figures stop short of pointing to omicron’s intrinsic transmissibility, as they compare omicron and delta from two contrasting states — the former is in the middle of a surge while the latter is on the decline.

But the results nonetheless indicate that omicron has a certain ability to sneak through protection developed by those who have been vaccinated as well as those who already caught the virus once, the team said. While the vaccination rate is low in South Africa at about 30%, many there acquired natural immunity after being infected with COVID-19.

An employee assists travelers at Narita Airport in Chiba Prefecture on Nov. 30. | BLOOMBERG
An employee assists travelers at Narita Airport in Chiba Prefecture on Nov. 30. | BLOOMBERG

There is no community spread of the highly mutated omicron variant confirmed yet in Japan, although it has been detected at airports in some travelers arriving from overseas.

A fourth omicron case was found Wednesday in a man in his 50s who arrived in Japan from Nigeria on Saturday. He is now isolated at a medical institution and reportedly asymptomatic.

The other 103 passengers on the same flight have been identified and their health conditions will be monitored, the health ministry said. The man received his first and second doses of Pfizer Inc.’s COVID-19 vaccine in October, it added.

The scientists' findings indicate that omicron could spread even in a highly vaccinated country like Japan.

“It’s very likely that (the variant) could spread in a country like Japan where vaccine uptake is high,” the professor said. A little over 77% of the country’s population has now been fully vaccinated, according to Our World in Data.

Advisory board head Takaji Wakita also sounded the alarm.

“Japan’s border restrictions are allowing it to buy time. Our previous experience suggests that we need to make preparations based on the assumption that there are bound to be (omicron) cases emerging domestically.”

Tokyo's Shimbashi district on Friday | KYODO
Tokyo’s Shimbashi district on Friday | KYODO

On Thursday, Prime Minister Fumio Kishida told parliament that the government is negotiating with Pfizer Inc. to “bring forward the schedule” for an additional supply of booster shots.

Pfizer and its German partner, BioNTech SE, said Wednesday a third shot of their coronavirus vaccine appears to offer sufficient protection against the omicron variant. While two doses may not be sufficient protection against omicron, that should still be enough to keep people from developing severe illness, the companies said.

Information from Kyodo added

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