As Hong Kong’s fifth wave of Covid-19 begins to stabilise, a top epidemiologist has said the city should decide between maintaining dynamic zero-Covid strategy or living with the disease.

However, Gabriel Leung, the Dean of the University of Hong Kong’s (HKU) Li Ka Shing Faculty of Medicine, said the decision was only “for the interim,” as co-existence with the virus would become the eventual “common pathway” globally. He said it would be “safer” for Hong Kong to complete the transition sooner rather than later based on scientific and public health grounds.

The University of Hong Kong. Photo: Kelly Ho/HKFP.

Leung laid out the possible benefits and challenges for the city to adopt either strategy during a press briefing on Tuesday morning.

According to the latest prediction from HKU’s epidemiological model, there could be about 4.5 million infections and 8,383 deaths by April 21, when the government plans to start the relaxation of social distancing measures. It is estimated that the daily case count will drop to three digits by then as well.

Zero-Covid not ‘totally impossible’

The first option, according to Leung, would be to continue the dynamic zero-Covid policy and “find the single last patient.” In that case, Leung said compulsory citywide testing would be “mandatory” and the city would have to prevent any imported cases from leaking into the community. Leung said the society could return to what it was like before the fifth wave if the virus was successfully cleansed from the city.

However, Leung said it would be “absolutely the first time” any place in the world had attempted to achieve zero-Covid following a large-scale outbreak. He said although the zero-Covid policy was implemented in mainland China and has been attempted by some eastern European countries, no one has tried it “at the tail-end of a very big wave.”

Gabriel Leung. Photo: Video screenshot.

Leung said the compulsory universal testing should only be rolled out when daily infection figures were at triple digits, as health authorities would have to arrange quarantine and treatment for all cases that were uncovered and conduct contact tracing.

“For every patient [tested,] you may need to put 100 others in quarantine.” Leung said, as he estimated that there would about five to 10 close contacts for each Covid-19 patient.

Leung said decision makers should also consider how to handle “long shedders,” or recovered patients who are no longer infectious but still return positive results. Leung said nucleic acid tests could not distinguish whether a patient carried a “live virus” that could infect others.

As some 4 million citizens were estimated to have been infected by late April, Leung said there would be “not a small amount” of long shedders, and authorities would have to decide how to deal with their close-contacts. Leung said the rumoured three-round citywide tests would be inadequate to spot all invisible cases.

Leung also added that the dynamic zero-Covid measures would be difficult to sustain as travel restrictions were less strict than before. He reminded the public that the fifth wave was caused by transmission within a quarantine hotel and the case leaked to the community and “went on to infect 4 million people.”

When asked whether zero-Covid was truly achievable, Leung said he did not think it was “totally impossible.”

Towards endemicity

Leung said the second option laying in front of the people of Hong Kong would be transition to “endemicity,” where the biggest objective will be to minimise severe cases, deaths and burdens to the health care system, rather than focusing on finding the single last patient in the community.

Caritas Medical Centre in Sham Shui Po, Hong Kong during the fifth-wave Covid-19 outbreak. Photo: Kyle Lam/HKFP.

He said society had to understand that the casualties could not be reduced to zero under this approach as “there will always be deaths when there are infections.” However, he said that the medical system would not be overwhelmed by fatalities.

If the second option is picked, Leung said that social distancing measures should evolve “dynamically” according to the situation in public hospitals. “They have to be tightened when signs emerge, such as beds running out in the Hospital Authority, and far before [health care systems] are overwhelmed,” Leung said.

Leung said universal testing or other forms of compulsory tests would become unnecessary and the resources could be reallocated to other aspects like increasing medical supplies and hospital beds.

Nonetheless, Leung noted that it would be challenging to keep the number of infections, hospitalisations and deaths at bay, while he said the public’s tolerance of casualties also needs to be taken into account.

‘A matter of time’

Leung said that while there may be political debates between the two available options, scientifically the difference between them was only “a matter of time.”

According to the epidemiologist, living with the virus will be the “common eventual path for the entire world” and whatever choice the city makes is “for the interim” only. He said no scientist in the world believed that Covid-19 could be driven back into the non-human population – the reservoir of bats – and that it was expected to exist in humans for the long term.

Leung said an “exit wave” was inevitable if a place was to relax its anti-pandemic restrictions and resume normality. “No matter if you reopen one, five, or 10 years later, [the exit wave] will come as a certainty.” Leung said, adding that the key was what could be done to minimise its impact.

Leung referred to dynamic zero-Covid as a “transfer station” and living with Covid as the “terminal station” and said the ultimate solution for the city to walk away from the emergency state of the pandemic could only be a controlled transition to endemicity.

In addition, Leung told reporters that Hong Kong has “passively” and “involuntarily” completed 60 per cent of its journey towards the second option, as around 60 per cent of the city’s population would be infected by the fifth wave according to HKU predictions.

Vaccination and medication

Both options, according to Leung, were “plausible” for the city to tackle the end of its fifth-wave outbreak. However, Leung said in his opinion that it would be the “safest” to push for the second approach “earlier rather than later,” provided that there is sufficient vaccination coverage and Covid-19 medicines available.

Leung said for the city to be eligible to live with Covid, the second dose vaccination rate among people aged 60 or over had to at least exceed 90 per cent. Meanwhile, Covid-19 oral drugs should be made accessible to all higher risk patients in the early days of infection.

During the press conference, HKU’s medical faculty released its latest empirical analysis of the effectiveness of the two available vaccines – the Chinese-made Sinovac and German-produced BioNTech – based on data of hospitalised patients in Hong Kong as of March 8.

According to their findings, receiving three jabs of a Covid-19 vaccine, irrespective of the brand, can provide around 98 per cent of immunity against severe or fatal cases in patients aged 60 or above.

HKU also used its model to estimate the impact of a possible sixth wave, assuming that the city will opt for full relaxation of social distancing measures on June 1 and transit into endemicity.

After taking into account the projected vaccination status and on the assumption that Covid-19 oral drugs were given to 56 per cent of patients in need – the amount distributed by the Hospital Authority in their first week of use – the university predicted that the sixth wave would last for two months, infecting some 2.21 million and killing 1,540.

According to the model, reopening to international travel would have little effect on transmission if arrivals are fully vaccinated and test negative before their departure.

Leung said they were not trying to make decisions for the city but were instead providing a scientific prediction to inform public deliberation. He also said science was only one factor to consider, with others including economy, people’s livelihood and tolerance, “or even politics.”

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Peter Lee

Peter Lee is a reporter for HKFP. He was previously a freelance journalist at Initium, covering political and court news. He holds a Global Communication bachelor degree from CUHK.