There has only been one infection recorded in each of the buildings over the past two weeks. Authorities previously warned they would carry out at least one lockdown per day until Lunar New Year.

Earlier on Friday, at least six residential buildings were put under ramped-up mandatory testing orders after each block recorded a case. The areas included private estates such as Block 9 of Gold Coast, and Carmel Cove Block 9 in Caribbean Coast in Tung Chung.

The coronavirus-hit construction site cluster at the airport’s third runway continued to expand, with two more confirmed cases linked to the group, bringing the number of patients involved to 24.

Separately, an engineering firm also reported that a worker had contracted the virus after he had contact with an infected colleague who was confirmed with Covid-19 while on a South Korea trip. Authorities are investigating possible links between recent infection clusters at construction sites.

A business traveller who was exempted from quarantine was also among Friday’s confirmed cases, despite testing negative for the virus in Shenzhen on January 21. But health authorities said the case would be treated as local transmission, as the patient had spent more than a week in the city upon arrival.

The latest developments came as 90 per cent of some 12,000 educators polled by the Hong Kong Professional Teachers’ Union (PTU) indicated they were angry that education authorities were asking schools to test teachers regularly as a condition to fully resume classes.

Education chief says Covid-19 testing for teachers not a condition for reopening schools

The vast majority also said the Education Bureau had provided either “insufficient” or “very insufficient” reasons in explaining why the number of students allowed back to school should be tied to the testing of teachers.

The survey, conducted between Thursday and Friday, received 11,822 responses from educators from kindergarten, primary and secondary schools, including 306 school principals and 196 vice-principals.

In calling for the bureau to scrap the testing demand, the 100,000-strong PTU called it an ineffective measure against the pandemic and a hurdle to fully restarting classes.

Union chairman Fung Wai-wah said members of the education community had closely followed health guidelines and arrangements on school closures and the holding of public exams over the past year, to prevent infection clusters that could put students at risk.

“The [testing] arrangement from the Education Bureau is voluntary in name, but in reality, it puts pressure on schools to comply,” Fung said, explaining the anger in the sector.

Fung also accused education authorities of announcing a testing arrangement that “lacked scientific backing” from health experts.

Among the school heads polled, some 90.4 per cent said they felt “some” or “a lot of” pressure because of the bureau’s plan, while 90.2 per cent said it presented administrative difficulties.

Hong Kong schools have been closed since December 2, and currently just a sixth of a school’s student body can attend lessons in the classroom.

The bureau on Wednesday said schools might expand face-to-face classes after the Lunar New Year holiday, but with just a third of all students attending half-day classes.

For all students to attend, schools would have to get their teachers screened for Covid-19 every two weeks.

On a Friday morning radio programme, Secretary for Education Kevin Yeung Yun-hung defended the decision for a second day in a row, reiterating that schools were “not required” to ask teachers to take the tests.

“Teachers are a relatively higher risk group given their daily activities. For instance, they need to talk quite a lot in classrooms and would [be in contact with] students,” Yeung said. “We are not saying that [teachers] taking the tests would mean there is zero risk.”

He said schools were merely being offered an option that would allow them to bring back the entire student population after Lunar New Year.

Sudden lockdowns leave some residents trapped in shops, hair salons overnight

“Schools have no [pressure]. We did not require schools to [take the virus tests],” he said. “Should we not let some schools take an additional step if they are willing to do so?”

The poll results came a day after another major teachers’ group, the Hong Kong Association of the Heads of Secondary Schools, slammed the plan as a waste of manpower and medical resources.

The association said that the bureau, along with relevant health authorities, should have issued a compulsory testing notice requiring teachers, staff, students and visitors to schools to undergo Covid-19 tests rather than putting the burden only on school staff.

“It is very undesirable to request schools to submit applications to the bureau for full resumption of half-day face-to-face classes,” the association said in a statement published on Thursday.

Meanwhile, only a single preliminary-positive coronavirus case was found after 2,160 residents in Yau Ma Tei were tested in the latest “ambush-style” lockdown, which was lifted on Friday morning. But authorities later clarified that the case was a recovered patient who had been discharged after showing a positive antibody response.

A smaller testing zone in Mong Kok showed no new infections after 70 people were screened, though three close contacts of previously confirmed cases were identified and sent to quarantine centres.

Separately, the government’s Expert Committee on Clinical Events Assessment following Covid-19 Immunisation held its first meeting on Thursday, and discussed a risk communication plan that included the monitoring, reporting and following up of adverse cases after the coming vaccination roll-out.

In a late night statement, the government also confirmed vaccine maker Sinovac will submit its third-stage clinical trial data collected in Brazil and Turkey, which it had earlier filed to the World Health Organization, to the city’s health authorities by the end of the week at the earliest.

The government’s expert panel on vaccines will then review the materials next week, kicking off the approval process for emergency use of the jab in the city.

Hong Kong has procured 7.5 million vaccine doses each from three manufacturers, but Chinese pharmaceutical giant Sinovac has yet to deliver its products – originally set for January – as well as to submit final-stage trial data to the city for regulatory approval.

Additional reporting by Chan Ho-him