TAIPEI (Taiwan News) — Classes have been canceled for 56 students at two elementary schools in Taipei City after a pilot and mother of two students was confirmed to have suffered a breakthrough infection of COVID-19.

A breakthrough infection is defined as a person who has tested positive for COVID-19 at least 14 days after they have completed the full vaccine schedule.

On Wednesday, Wang Fang Elementary School in Taipei's Wenshan District and Taipei Municipal Jian'an Elementary School in Da'an District suspended classes as a precaution after the mother of one student at each school tested positive for COVID-19, despite being fully vaccinated.

Health Minister and CECC head Chen Shih-chung (陳時中) on Wednesday morning (Oct. 6) confirmed the woman was a pilot for China Airlines (CAL) who had undergone the mandatory five days of quarantine and nine days of self-health monitoring. Chen said that she had two doses of a COVID-19 vaccine before entering quarantine and therefore is classified as a breakthrough infection.

The head of Zhongzheng District Health Center, Zhang Hui-mei (張惠美) said the woman's two children attend Wang Fang Elementary School and Taipei Municipal Jian'an Elementary School. As each child attends a class of 28 pupils in each school, a total of 56 students were affected by the class suspensions.

During a press conference on Wednesday afternoon, CECC Spokesperson Chuang Jen-hsiang (莊人祥) identified the woman as case No. 16,377, a China Airlines pilot in her 40s who received her second dose of the Moderna COVID-19 vaccine in early August. From Sept. 23-26, she served as a crew member on flights to and from Anchorage, Alaska.

From Sept. 27 to Oct. 1 she underwent quarantine at a company dormitory in Taiwan. From Oct. 2-3, she stayed at her home, where she came in contact with her family members.

On Oct. 3, she was aboard a round-trip flight to Singapore that returned to Taiwan that day. As part of the 5+9 days of quarantine and self-health monitoring rule for long-haul flight crews, she was tested for COVID-19 on Oct. 5 and the result came back positive.

Chuang said the woman had tested negative for the virus in June, July, and August. A test taken on Oct. 1 also came back negative, but the test taken on Oct. 5 was positive with a Ct value of 33.

Under the 5+9 system, flight crews must undergo PCR testing on the fifth, ninth, and 14th days after returning to the country.

The spokesperson stated that a second test administered on the woman on Oct. 6 also came back positive, with a Ct value of 22. Chuang said that she tested positive for n antibodies and negative for s antibodies, indicating that it is a recent infection.

Thus far, the health department has identified six contacts in her case, including four family members living with her and two coworkers. PCR tests administered on these contacts have come back negative, while the health department continues contact tracing in the workplace.

As to whether the woman contracted the virus while flying to the U.S. or to Singapore, further investigations are required, said Chuang. According to the Civil Aeronautics Administration, 98.7% of flight crews that serve on international flights have been fully vaccinated.