Coronavirus: Hong Kong on 40-day streak of no untraceable cases after policeman’s false positive down to possible contamination

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Hong Kong marked 40 straight days without a single untraceable case of Covid-19 locally after a policeman whose reported infection snapped the long streak the previous day turned out to be officially coronavirus-free on Wednesday.

The mistaken diagnosis was blamed on confusion caused by suspected contamination of a sample taken from the officer at a clinic – the sample had tested positive multiple times, but he returned a negative result each time he was subsequently tested again in hospital.

An expert involved in the investigation urged clinics to ensure a clear division of labour for processes such as the handling of used vaccine bottles and specimen collection kits, to reduce the number of such incidents.

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Health authorities on Wednesday confirmed just one imported Covid-19 case, involving a 58-year-old man who arrived from the United Arab Emirates. The city’s overall tally stood at 11,848, with 210 related deaths.

The Centre for Health Protection said genetic analyses by its own laboratory as well as the University of Hong Kong’s department of microbiology confirmed the 35-year-old officer, who was attached to the patrol subunit of the force’s Wan Chai division, carried a virus that was “compatible” with a vaccine strain.

“After examining the clinical, epidemiological and laboratory findings, the case is compatible with vaccine strain contamination and hence will not be classified as a case of Covid-19 infection,” a statement from the centre read.

The government’s quarantine centre at Penny's Bay. Photo: Dickson Lee
The government’s quarantine centre at Penny's Bay. Photo: Dickson Lee

Professor Yuen Kwok-yung, an infectious disease expert from the University of Hong Kong, on Wednesday assured the public that the incident was a false alarm, after inspecting a Lok Fu clinic where the officer had visited, the Prenetics laboratory that processed his samples and the Central Library community vaccination centre that he had been to.

“We are very confident that Hong Kong has remained free of local untraceable cases for the 40th day,” Yuen said.

The expert and health authorities said five samples collected from the officer from Monday to Wednesday during his hospital stay all tested negative, and none of his close contacts had returned positive results for the coronavirus. These raised doubts over the man’s infection status.

“The samples first sent to Prenetics had a very high viral load … but the virus could not be found on him after he was sent to hospital,” Yuen said.

He added the policeman could have obtained a contaminated specimen bottle from a Lok Fu clinic where four people had received Sinovac jabs earlier that day. A nurse at the clinic had probably touched the bottle after administering the shots and transferred “dead” RNA material to the policeman’s specimen kit, according to Yuen.

“When a vaccine is extracted from a vial, some traces might fall out as drops on the side of the bottle,” Yuen said. “When the nurse removed the vaccine vial label and attached it to a patient’s medical record, their hands might have came into contact with the inactivated virus from the vaccine … Then when the nurse handed the collection kit to the policeman, the virus traces could have been transferred.”

Yuen noted even small amounts of vaccines contained very high levels of viral RNA, the genetic material of a virus, and this could cause contamination.

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The expert urged clinics providing Covid-19 vaccines to ensure a clear division of labour and prevent nurses involved in the inoculation process from handling specimen bottles.

The clinics should also be sanitised with bleach every evening after closing, he added, as hand sanitisers could kill the coronavirus but still leave RNA material on surfaces or people’s hands.

Environmental samples were collected from various spots of the clinic in question, and test results are expected to be out by Thursday at the earliest.

While the officer had shown symptoms such as sore throat and cough since last Friday, Yuen said he believed these could be caused by the rhinovirus or parainfluenza virus, pathogens found in his children but not on him. Yuen suggested the officer could have been infected by those viruses, but his adult immune system would soon eliminate them.

A total of 49 close contacts of the officer have been identified, and authorities said they would be released from quarantine if they tested negative for the virus. A police source said arrangements were being made for some 30 of the officer’s colleagues to leave the camp.

The case was the second such incident of a mistaken infection later found to be caused by sample contamination from a vaccine.

Last Thursday, a 61-year-old nurse who worked at a community vaccination centre at Kwun Chung Sports Centre had her infection discounted after genetic analysis came back showing similarities between her respiratory specimen and the coronavirus vaccine strain.

Meanwhile, Yuen voiced disagreement with a new government decision not to reveal the deaths of those who had received the shots but whose cases were unlinked to vaccines.

“The information should be announced, but details should also be included on whether unvaccinated people suffered similar problems, and how many had such conditions,” Yuen said.

But Professor Ivan Hung Fang-ngai, co-convenor of a government expert panel in monitoring the Covid-19 vaccine roll-out, supported the latest change.

“Previously we have been too transparent and done too much … one unfortunate condition happened: the public reckoned that vaccination was related to deaths,” Hung said. “It was one of the critical factors why the vaccination rate has remained low.”

Additional reporting by Clifford Lo and Lilian Cheng

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