Health authorities may take blood samples for coronavirus antibody testing from arrivals at Hong Kong’s international airport under a proposal aimed at shutting out dangerous new variants, as the city tries to stave off a potential fifth wave of infections.
Chief Executive Carrie Lam Cheng Yuet-ngor on Tuesday said she supported the idea, also revealing that her government was considering ways to make it convenient for children to get vaccinated now that an advisory panel had backed extending the city’s inoculation programme to those as young as 12.
With just over 15 per cent of 7.5 million Hongkongers having received both vaccination doses until now – far short of the government’s 70 per cent target to achieve herd immunity – the private sector has been offering incentives to boost the take-up rate.
Do you have questions about the biggest topics and trends from around the world? Get the answers with SCMP Knowledge, our new platform of curated content with explainers, FAQs, analyses and infographics brought to you by our award-winning team.
Tycoon Li Ka-shing’s companies and charity foundation joined the list on Tuesday, saying they would give out HK$20 million worth of shopping coupons through raffles.
In a continuing reflection of Hong Kong’s progress in tackling the pandemic, authorities confirmed three new Covid-19 cases – two brought in from Colombia and one from Indonesia. The city’s total number of infections now stands at 11,868, with 210 related deaths.
Hong Kong is also closely monitoring a continuing outbreak in neighbouring Guangdong province. Medical experts a day earlier warned that loopholes identified in travel arrangements and lax enforcement of testing rules for Hongkongers returning from mainland China could put the city at greater risk.
On Monday Guangdong confirmed 19 new infections, 14 of them from the provincial capital of Guangzhou.
For international arrivals, experts have suggested antibody tests to show whether they are protected by a Covid-19 vaccine. Such tests can also help identify false negative cases during quarantine to ensure that those who are asymptomatic are not released into the community.
“[Experts have said that] apart from requiring them to be tested for the coronavirus and have two doses of vaccine, they should also be tested for antibodies. I agree with this in principle. It is always good to add more protective nets,” Lam said on Tuesday.
“I know that the Centre for Health Protection is studying at which point this should be introduced, and which testing method should be used.
“We need to consider how to do this so it matches our requirements for health protection without causing greater inconvenience to those affected. We will study this seriously.”
The testing methods under “close study” involve drawing blood with a syringe or a finger prick.
David Hui Shu-cheong, an expert from the Chinese University of Hong Kong who advises the government on the pandemic, said a finger-prick test could deliver results in just 20 minutes, but he suggested running a comparative study of the technique’s sensitivity against the blood-drawing method before any roll-out of the airport testing scheme.
Another antibody test could be performed at the end of the 21-day quarantine period for arrivals before releasing them into the community, he added.
Infectious disease expert Dr Leung Chi-chiu told the Post he believed antibody tests could catch some cases in those carrying the virus that were not detected by polymerase chain reaction (PCR) screening.
“The upper respiratory tract is a large area, and sometimes, owing to the timing or sampling technique, you may not be able to swab the virus in the PCR test, therefore producing false negative results,” he said.
Serology tests that screen for the existence of antibodies in blood would have less of a sampling problem.
Leung suggested placing self-isolating individuals who had tested positive for antibodies under more active surveillance, including monitoring of symptoms and even more frequent PCR testing, as they might finally yield a positive result upon more accurate sampling.
“Now that daily caseloads are low, we can do more at the border,” Leung said.
Neighbouring Macau has from Saturday required arrivals from Brazil, India, Nepal, Pakistan and the Philippines to provide proof of either vaccination or a negative antibody test, on top of three negative PCR ones taken in the week before departure.
Hong Kong bans the entry of travellers who have stayed in those five countries plus South Africa for more than two hours in the preceding 21 days.
Boston Logan International, Istanbul, Istanbul Sabiha Gokcen, John F. Kennedy International, London Gatwick, London Heathrow, London Luton, London City, Munich and Newark Liberty International are among the airports providing antibody tests along with other screening options as an entry requirement.
On Monday, Hong Kong health authorities confirmed another case of the Alpha variant, first identified in Britain. The 20-year-old woman – the sister of a teen previously identified as carrying the variant – was the sole local infection that day.
Lam conceded the emergence of coronavirus variants indicated cracks in the city’s pandemic-control measures.
“But these cases being missed does not mean that there are big loopholes in our policies,” she said.
“For the coronavirus, there is no definite answer as to exactly how long the incubation period can be, and Hong Kong’s measures may be the strictest in the world, as we have 21 days [of quarantine].”
The chief executive added that recent developments had made it even more crucial for Hong Kong residents to get vaccinated.
Additional reporting by Chris Lau
More from South China Morning Post: