The Japanese city of Kobe announced on Tuesday that it has confirmed for the first time a COVID-19 case of a mutant called "E484Q" that may weaken the effect of the vaccine, Kyodo News reported.

A male over 50 years old tested positive for the strain on May 17. He was mildly ill and completed his medical treatment at home 10 days later. Genomic sequencing of the virus found that it belongs to the mutated variant.

About 150 cases of the mutant strains similar to this one have been found overseas, mainly in Europe, according to local authorities.