TAIPEI (Taiwan News) — The Central Epidemic Command Center (CECC) on Thursday (Sept. 2) announced Taiwan's first confirmed case of the Mu variant of COVID-19, a Taiwanese woman who had received two Pfizer vaccine doses in the U.S.

The World Health Organization (WHO) on Monday (Aug. 30) added the Mu variant (B.1.621), which has been detected in 39 countries, to its variants of interest (VOI) watchlist. At a press conference on Thursday, Philip Lo (羅一鈞), deputy head of the CECC’s medical response division, announced that an imported COVID case had been found to be infected with the strain, which originated in Colombia.

Lo pointed out the variant appears to have multiple mutations in its gene sequence that may enable it to escape vaccine-induced immunity. He said that further observation is needed to determine whether the variant has developed a resistance to vaccines.

Lo explained that Taiwan's first case of the Mu variant, case No. 15,858, was originally diagnosed with COVID-19 on Aug. 13. According to Lo, the infected person is a Taiwanese woman in her 60s who had returned from the U.S. in early August.

She had received the first dose of the Pfizer vaccine in the U.S. on July 5 and the second on July 26. When she returned to Taiwan on Aug. 3, she did not report any symptoms, but a test administered at the airport revealed that she was positive for COVID, with a Ct value of 29.

When the CECC scientists carried out genetic sequencing on the virus, they found it was the variant that started in Colombia, but at the time the WHO had not yet given it a designation based on the Greek alphabet. A retrospective investigation carried out this week confirmed that it was what is now known as the Mu variant.

The woman has since recovered and been released from quarantine. Research by the WHO has found that of the 39 countries reporting cases of the Mu variant, the U.S. has the most at 2,065.