The study references the opening up policies of the United States, Britain, Israel, Spain and France. I offer a summary here but urge you to read it yourself. It involves a bit of high school maths, which you can probably work out yourself. It shows such factors as population size and density, the disease’s transmission rate and the state of public health facilities that must be taken into account before deciding on a policy.

China’s countrywide population density is 147 people/km squared; and that of the eastern most populated region – Hebei, Shandong, Jiangsu, Zhejiang, Fujian, Guangdong, Hainan, Beijing, Tianjin and Shanghai – is 661 people/km squared. The full vaccination rate of the entire population is roughly 55.04 per cent.

All the countries referenced have a higher vaccination coverage and greater natural immunity than China. The US, Spain and France have population densities lower than China; none of the referenced countries have population densities as high as that of the eastern region of China. Therefore, right from the start, switching to opening up automatically puts China in a worse state than those other countries, each of whose success is being called into question.

The researchers then used standard dynamic transmission models in epidemiology to see what might happen if China were to have a lower population density and high immunisation and natural immunity rates comparable to those of the referenced countries.

Could China have tolerated a higher infection rate within the population provided that severe cases of Covid-19 have been substantially reduced under large-scale vaccination, which would prevent the medical system from being overrun? That is, incidentally, the policy of British Prime Minister Boris Johnson, the target of hostility, even hatred, of many public health workers.

No, the models show that even with the improved “lower bound” conditions, China would still have it worse opening up because of its overall large population and relatively scarce health resources per capita.

But the opening up/living with Covid strategy has been called into doubt even in many Western countries. For it to work, there has to be not just high vaccine coverage, but also high vaccine protection efficiency. The Delta strain and now Omicron variant, and future variants that will almost certainly emerge, make this strategy difficult to pursue in China.

Interestingly, while Western critics slam China for not following their health strategies, the Peking University wrote this typically Chinese statement: “Our suggestions towards China might not necessarily be applicable to other countries.”

Their study concludes: “The estimates revealed the real possibility of a colossal outbreak which would almost certainly induce an unaffordable burden to the medical system.

“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.”

It adds that the epidemic can exponentially decline (as with what happened with Covid-19 in China last year) or explode (possibly if China opens up now).

“According to the celebrated dynamic models in epidemiology and Gronwall’s inequality in maths, an epidemic decays exponentially when the reproductive number R<1, but may also blow up in the same exponential manner once R>1.

“In the past year, many in the world have suffered by overconfidently jumping into the latter scenario. China should not, and cannot afford to, be the next.”