A group of Chinese mathematicians have offered a "clear warning" about the devastating impacts of the country abandoning its zero-tolerance Covid policies.
The study, conducted by mathematicians at Beijing's Peking University, found China could face more than 630,000 daily Covid infections if it lifted its strict travel restrictions.
The report was recently published in the in China CDC Weekly by the Chinese Centre for Disease Control and Prevention and used data from multiple countries to determine the Covid threat they would face if restrictions were eased.
The group used data collected in August from the United States, Britain, Spain, France and Israel to determine how China's Covid situation would be impacted if it adopted each of these country's infection policies.
The study showed China would fare the worst under the pandemic strategies used by the US, with cases predicted to rise to more than 637,000 a day, a monumental increase from the 23 new cases detected on November 27.
This estimation also includes about 22,300 severe cases of the disease.
If China adopted the UK's Covid strategy, cases could rise to more than 275,700 a day, with 9,680 of those severe infections.
Under France's Covid strategy daily cases are estimated to rise to 454,000, under Israel's policy daily cases would be around 442,200 and under Spain's strategy daily infections would be just under 320,000.
The mathematicians said the estimates revealed the "real possibility of a colossal outbreak", which would put the country's medical system at risk of being overwhelmed.
"Our findings have raised a clear warning that, for the time being, we are not ready to embrace 'open-up' strategies resting solely on the hypothesis of herd immunity induced by vaccination advocated by certain western countries," the study states.
China currently has some of the strictest border and quarantine measures in place for international travellers.
The policies for international arrivals involve long quarantine stays, strict Covid testing measures and submitting a raft of forms, test results and declarations to respective Chinese embassies just to board the plane.
The study found a combination of more efficient vaccinations and specific Covid treatments would be needed before travel restrictions can be eased.
The experts also said retaining flexible non-pharmaceutical interventions (NPIs) and strong tracing and isolating measures for Covid cases would also be key to reopening safely.
They also noted the emergence of the Omicron variant could potentially impact the effectiveness of the Covid vaccines.
"There have been recent arguments that a higher infection size is now more tolerable provided that severe cases of Covid-19 have been substantially reduced under the large-scale vaccination campaign, preventing the medical system from being overrun," the study notes.
"While vaccination has been proved to significantly reduce the development of severe symptoms after infection from the original and mutated strain of the virus, the emergence of new mutated strains would potentially disrupt such protection."
On Friday, the World Health Organisation (WHO) declared Omicron, which was detected in South Africa earlier this month, to be a "variant of concern".
The classification put Omicron into the most troubling category of Covid-19 variants, along with the globally dominant Delta, and its weaker rivals Alpha, Beta and Gamma.
Cases of the new variant have now been detected in South Africa, Botswana, Hong Kong, Belgium, Germany, Italy, the Czech Republic, the UK and Australia.
NSW Health confirmed the new cases on Sunday afternoon, with two passengers testing positive to the new variant after arriving in Sydney from southern Africa on Saturday night.
The detection of the new variant has prompted several countries to impose strict travel restrictions on travellers from southern Africa, including Australia, Brazil, Canada Iran, Japan, Thailand, the US and the UK.
The restrictions prompted South Africa to complain it was being unfairly hit with "draconian" air travel bans for having first detected the strain.