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Models predict massive wave of disease and death if China lifts ‘zero COVID’ policy

Country’s severe approach to pandemic is inflaming the populace, but lifting it carries huge risks

People protest zero COVID measures by holding up empty sheets of paper
People in Beijing hold up empty sheets of paper to protest China’s COVID-19 restrictions on 27 November.thomas peter/reuters
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A version of this story appeared in Science, Vol 378, Issue 6624.Download PDF

Surprised and stung by protests against draconian “zero-COVID” policies, Chinese authorities are gingerly moving to ease the burden of lockdowns, quarantines, and constant testing. But 3 years into the pandemic, China shows no sign of planning a major course change. Mathematical models suggest why: The country is still ill-prepared for living with SARS-CoV-2. Easing restrictions today would likely trigger a massive wave of infections, overwhelm health care facilities, and bring a high death toll.

“China has not achieved high vaccination rates, has not used the best type of vaccines, and it has been very slow in communicating [to the public] the eventual need to transition from elimination to suppression and mitigation,” says public health scientist Nick Wilson of the University of Otago, Wellington, in New Zealand. Other countries that initially followed the zero-COVID strategy, including New Zealand, used it to buy time to ramp up vaccination rates, stockpile antivirals, and boost intensive care capacity.

The fierce protests have triggered some changes. Several provinces have started to allow people to enter public transportation, restaurants, and shopping centers without proof of a negative COVID-19 test, for example, and some close contacts of patients will be allowed to isolate at home instead of being sent to quarantine centers. Those measures are “a small but important step, and I believe more steps will follow,” says a Chinese scientist who asked to remain anonymous. “This will alleviate some of the pandemic fatigue and reduce the burden on the economy and society.”

But models show why the Chinese government still wants to keep a lid on. A study based on vaccination rates in March, published in Nature Medicine in May, found that lifting zero-COVID restrictions at that point could “generate a tsunami of COVID-19 cases” over a 6-month period, with 112 million symptomatic cases, 2.7 million intensive care unit (ICU) admissions, and 1.6 million deaths. Peak demand for ICU beds would hit 1 million, more than 15 times the current capacity.

The unvaccinated would account for 77% of the fatalities, according to the authors, primarily at Fudan University. Boosting vaccination rates could slash the toll, but China’s elderly population has remained wary of vaccination. Even today, only 66% of those ages 80 and older have received two doses—versus 90% of the population as a whole—and just 40% have taken boosters.

Hong Kong provides a cautionary tale: A big Omicron outbreak early this year caused nearly 6000 deaths, 96% of them in people 60 or older. At the time, Hong Kong’s vaccination rates were even lower than the mainland’s. In the first 3 months of this year, the city had a COVID-19 death rate of 37.7 per million population, among the highest anywhere.

A new study released on 28 November by Airfinity, a London-based health analytics firm, suggests mainland China remains vulnerable. Lifting zero COVID now could cause between 167 million and 279 million cases and between 1.3 million and 2.1 million deaths over 83 days, according to the report.

Besides being underused, China’s vaccines—which contain inactivated virus—are less effective than the messenger RNA (mRNA) vaccines available elsewhere. A study in Hong Kong, where people could choose between the Pfizer-BioNTech mRNA vaccine or CoronaVac, a Chinese vaccine, showed three shots of either were more than 90% effective in preventing serious illness and death among those older than 60. But two doses of the mRNA vaccine were significantly more effective than two shots of CoronaVac. A separate study suggested CoronaVac’s protection wanes more rapidly.

In May 2021, BioNTech and China’s Shanghai Fosun Pharmaceutical agreed to set up a 50-50 joint venture to make and sell BioNTech’s shot in China. But the product never received regulatory approval, perhaps to protect China’s homegrown vaccines. Four Chinese companies have mRNA vaccines in various stages of development, but none has received the green light either. Pfizer’s COVID-19 drug Paxlovid is available in China, as is a locally produced monoclonal antibody therapy, but it’s unclear how many doses the country has.

Mainland authorities are still hoping to boost vaccination rates among the elderly. A 29 November directive of the National Health Commission urged local authorities to set up teams to go door to door and assess whether the ill and infirm can be safely vaccinated, and to launch education campaigns to counter vaccine hesitancy.

But those efforts will take time, says Xi Chen, a public health scientist at the Yale School of Public Health. “Reopening too soon will crowd out resources, crush the medical system, and cause more deaths,” he says. For now, China remains trapped in the Catch-22 of its own making.

Update, 10 December, 8:15 a.m.: Soon after this article appeared, China’s national government announced that the relaxation of zero-COVID restrictions being adopted by some localities should apply nationwide. Most COVID-19 testing will be dropped, except for those working in health care facilities and schools; close contacts and asymptomatic and mild cases will be allowed to isolate at home, though they will be subject to testing; and smartphone health status codes will no longer be checked for travel within China. Now, “It will be extremely difficult to go back to the zero-COVID policy,” says Xi Chen, a public health scientist at the Yale School of Public Health. He notes that mentions of zero COVID have disappeared from National Health Commission press releases.
Still, authorities are not entirely abandoning COVID-19 countermeasures. Local authorities are still authorized to impose lockdowns, though they are supposed to be limited in extent and duration. Travelers entering China still face a quarantine of at least 10 days. “Health officials warn that they will closely watch trends in deaths and adequacy of medical resources in case a return to tougher measures is needed,” Chen says.

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