A large-scale antibody study should be carried out to gauge the true number of Covid-19 infections in Hong Kong, information that would allow the government to make better-informed policy decisions, a veteran virologist has urged.
The recent return of Hongkongers from overseas has fuelled a rise in the number of cases to close to 900, but Malik Peiris, chair professor of virology at the University of Hong Kong, told the Post he believes the actual number could be higher, and called on the government to offer stronger support for research.
His call comes as the administration has been criticised for its indecision and lateness in closing down hotspots like pubs and mahjong parlours to contain the spread of local infections.
Peiris said many infected with Covid-19 had mild symptoms or even none, and therefore have not been detected by the health care system.
“The only way to find out how big the iceberg is by serological testing,” he said in recent interview.
Serological testing refers to blood tests that look for antibodies to the virus, which usually develop three to four weeks after infection.
Unlike the polymerase chain reaction (PCR) test currently used to identify infected cases, serological tests can tell whether an infection had taken place even after a person has recovered and no longer carries the virus.
Dr Robert Redfield, director of the US Centres for Disease Control and Prevention, last week said as many as 25 per cent of infected people were asymptomatic
While stressing the importance of ongoing PCR testing to diagnose infected patients for isolation, Peiris said testing for antibodies will give scientists a clearer estimation of the epidemic’s severity.
The findings would also shed light on the extent to which people are immune to the virus and whether so-called herd immunity – a form of indirect protection achieved when a large percentage of the population has become immune – had been reached.
That knowledge, Peiris said, would have policy implications.
“If [the authorities] know what the herd immunity is in a population, they can be much more confident in opening up the economy,” he said.
For example, if about half the population of Hubei province, which recorded the highest number of cases in China, were found to be immune, the authorities would be confident in rapidly scaling the economy back up, Peiris said.
“If only two per cent [of people were immune], then the risk of a re-emerging epidemic is very true and very real,” he said.
While he doubted Hong Kong’s population had yet achieved herd immunity, he said the situation would not be grasped completely until a study was commenced.
Similar antibody studies were carried out in 2009 as the city tackled the swine flu outbreak.
Those studies found about 40 per cent of children in Hong Kong were infected, though many had only mild symptoms. On the other hand, the elderly, who had a lower chance of becoming infected, were likely to develop more severe symptoms if they contracted the virus.
“We would know which age group had more herd immunity than others … who are the highest-risk groups,” he said, citing the experience 11 years ago.
But while scientists around the world are racing to develop drugs and vaccines for the new coronavirus, Peiris said support from the Hong Kong government had been “quite slow”, adding no specific funding had been injected into Covid-19 research.
He said researchers had to use previous funding for other purposes to cover the research costs.
“Government should rapidly mobilise research funding to these groups in an emergency such as this, rather than following routine bureaucratic procedures,” he said.
He said that Hong Kong researchers had repeatedly shown to be “world-leading” when it came to new epidemics, and the quick provision of funding would be crucial for a timely response.
“Without investigating a new outbreak, how can you know how best to respond?” he asked.
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