Aug 07, 2021 06:02 PM

Opinion: As Delta Spreads, Does China’s Virus Strategy Need a Rework?

Residents are vaccinated in Nanjing, East China's Jiangsu province, on July 16. Photo: VCG
Residents are vaccinated in Nanjing, East China's Jiangsu province, on July 16. Photo: VCG

This latest coronavirus outbreak in China, dominated by the highly infectious delta variant, has spread to at least 28 cities in 15 provinces since July, becoming the largest scale transmission since the Wuhan outbreak of early 2020.

The delta variant has triggered heated debate about the need to recalibrate disease control measures aiming to completely eliminate Covid-19 cases.

As the pandemic continues, the whole world will face one common issue — “pandemic fatigue” — said Feng Zijian, a research fellow with the Chinese Center for Disease Control and Prevention (China CDC), in a recent interview.

Provided the disease does not spread more widely, China’s existing control measures remain effective, Feng said. But sooner or later, adjustments to the current core strategy of “guarding against inbound cases and domestic resurgences,” including restrictions on the number of inbound travelers, nucleic acid tests for inbound travelers and quarantine measures, will be necessary.

Minutes of a meeting circulated online have revealed the views of Zeng Guang, a chief epidemiologist at China CDC, on the delta variant. He said that compared to the original coronavirus, the strain is 10 times harder to control, posing a huge challenge to China’s “zero-case” strategy.

According to the minutes, Zeng offered suggestions on vaccination strategy, including a third “booster” dose of existing inactivated vaccines used in China, and sequential or mixed vaccination using different vaccines.

He also said a change of perspective on pandemic control was needed, including a shift of focus away from eliminating the virus and infections entirely. The “zero-case” strategy will lose efficacy in the long run, he said, according to the minutes. Completely wiping out the coronavirus would be impossible. Ordinary control measures should be adopted.

On Aug. 4, Zeng verified these minutes for our Chinese science and current affairs website, The Intellectuals, but claimed that their release had not been authorized.

We asked four experts for their views on the delta variant and the best strategy going forward. They are columnist Zhou Yebin, who holds a doctorate in genetics; Jin Dongyan, a biomedical professor at the University of Hong Kong’s faculty of medicine; Chen Yu of the Wuhan University College of Life Sciences and a member of the university’s state key laboratory of virology; and Li Bin, director of the Popularization of Science Committee at the Chinese Society for Cell Biology, and a research fellow at the Shanghai Institute of Immunology. Their comments have been edited for clarity and length.

China has introduced the world’s toughest control measures to guard against the spread of the virus. Why has the delta variant been detected in many Chinese cities?

Jin Dongyan: It’s no surprise that over ten provinces and municipalities reported local transmission; they arose from imported cases that weren’t detected. We missed the first opportunity to stop it; we must focus on the remaining opportunities.

In general, these outbreaks can be brought under control. What’s more, the public remains alert and our “radar” system is working. Most chains of transmission are broken and put under control in time; otherwise, the flair-up would already be out of control.

Some people say that the R0 (transmission coefficient) of the delta variant is 6 to 8, similar to chickenpox. But what they fail to mention is that only a small proportion of people, about 10%–15%, have the potential to become superspreaders. That R0 reflects that the delta variant spreads faster than earlier strains, and causes more severe illness. However, for Covid-19, the key is to prevent superspreading events rather than focusing solely on the R0.

During this wave, the delta variant did cause a superspreading event at one point. Superspreading events are when many people — perhaps tens of people, or even over 100 — are infected at once, typically by a single individual. Preventing superspreading events is vital to controlling Covid-19.

Individual circumstances are one cause of superspreading events. For example, infected people with an immune deficiency or underlying disease may release a larger viral load, infecting more people. But that won’t be true of everyone. Some research suggests about 90% of the viruses spreading in the community come from about 2% of infected people, and that some 20% of infected people release 80% of airborne particles. Shouting releases 50 times more virus particles; singing about 99 times more.

In addition, certain conditions can cause superspreading; the Japanese call these the 3Cs: “closed spaces,” “close-contact settings” and “crowded places.” Studies show that restaurants, cafes and gyms are the places where Covid-19 transmission is most likely. Some 80% of infections occur in 10% of locations. In other words, managing these places well could help significantly.

How are existing vaccines’ efficacy rates changed by the delta strain? Does the emergence of a breakthrough infection mean that we need to develop a new generation of vaccines, or will need booster shots?

Chen Yu: Various research has indicated that the delta strain is capable of immune escape, reducing the efficacy of existing vaccines. So developing a new generation of vaccines, or having booster shots, will be necessary.

Relevant institutions throughout the country — including vaccine R&D institutions, manufacturers, drug evaluation centers and others — must speed up their R&D concerning vaccines targeting mutant strains, especially the key points that led to the delta strain’s relatively serious immune escape, and accelerate the marketing and deployment of these second-generation vaccines.

Moreover, a third vaccine dose should be given nationwide, preferably one that targets mutant viruses.

Jin Dongyan: Hong Kong tried mixing vaccines very early: Vaccines from two brands — Comirnaty [the brand name of the mRNA vaccine developed by BioNTech and Pfizer] and Sinovac — were given. Regardless of the order of which vaccine was taken first, the results were good.

It is imperative to increase vaccination coverage. In China at the moment, in addition to inactivated vaccines such as Sinopharm and Sinovac, and the vaccines from CanSinoBIO and Zhifei, 100 million doses of Comirnaty-branded anti-COVID-19 vaccines, imported by FosunPharma are also available, but Comirnaty has not yet been approved for this market.

The Phase 3 trials of Comirnaty were finished a long time ago. Perhaps the domestic trials are not yet completely finished, but this is urgent. This type of vaccine has been approved almost globally for emergency use, and has been very effective overseas, as well as in Hong Kong and Taiwan. According to the research data, the antibody levels this vaccine induces are several times higher than Sinovac’s and Sinopharm’s. But Comirnaty has not been approved in China.

If racial differences are so important that clinical trials for different races have to be conducted separately, then they should be conducted promptly and approval given as soon as possible. That way one dose of Comirnaty vaccine can be given to medics and nursing home residents, which will be more effective than giving them the third dose of the inactivated vaccines. Moreover, some preliminary studies show that CanSinoBIO works well combined with other vaccines. The better we protect vulnerable groups, the less danger we will face.

This time around, the source of the pandemic is cases imported from abroad. If the situation in other parts of the world does not improve, will it be impossible to achieve the goal of eliminating the virus that causes Covid-19 in China?

Zhou Yebin: Because Covid-19 is a global pandemic, for a single country to completely eliminate it within its own borders will be very difficult. It may be possible to suppress it domestically for a while, but longer term, particularly if the global pandemic does not improve, maintaining that will be very unlikely, if not impossible.

It’s not just China facing this problem; countries such as Australia and Singapore are in a similar situation. Through strict border epidemic prevention and control measures and entry quarantine, they, like China, achieved almost zero new cases at some point, but haven’t been able to maintain that situation for long.

We’re probably going to be living with this virus for a long time. That’s not because the vaccines aren’t good enough, but because the pandemic is just too severe on a global scale. More than 200 million people worldwide have been infected, with more than 200,000 new cases per day. That means the virus is still spreading. It will be very hard to wipe it out.

One viewpoint is that a “zero case” strategy is no longer realistic. Influenced by “pandemic fatigue,” governments in places like Singapore and the UK have relaxed restrictions. Will China ever treat Covid-19 in the same way it treats flu?

Jin Dongyan: Whether China will treat Covid-19 as it treats flu will depend on the data on its transmissibility, pathogenicity, and so on.

The UK’s Covid-19 mortality recently fell to a level similar to that of flu, so most pandemic-related restrictions were relaxed. [Editor’s note: England removed nearly all restrictions on July 19, eliminating social distancing requirements, limits on attendance at public events and also the strict requirement to wear face masks in most public places.]

For China to view Covid-19 in a similar way to the flu, several problems must be overcome.

First, China’s vaccines must be improved. Our vaccines are indeed effective, especially in the prevention of severe cases, but they are not the best in terms of protective capability. As a result, many medical workers remain at risk of infection even if they have received domestically produced vaccinations.

There have already been cases amongst cleaners and care workers in hospitals in Zhengzhou, and amongst doctors in hospitals in Guangzhou. We have to analyze the data, and check whether the newly-infected people had been vaccinated, rather than dodging the question by saying “no vaccine can guarantee protection from infection.” Pfizer’s vaccine is incapable of completely preventing infection, but its ability to protect, prevention rate and production of neutralizing antibodies are all clearly a bit better.

Second, we should keep the target population protected. During the pandemic period, all countries have given priority to protection of nursing homes, because COVID-19 causes high mortality rates if elderly people in nursing homes get infected. For example, more than 200 people have died of COVID-19 in Hong Kong; of those; over 100 of those were elderly people living in nursing homes. Without those deaths, far fewer people would have died.

There is a very big difference between the flu and Covid-19. The mutation rate of influenza viruses is about 5–10 times higher than that of the Covid-19 virus, so people need annual influenza vaccinations. But over the past year and up until now, the Covid-19 virus has changed little. Its mutation rate is slower than influenza viruses.

The virus strain that caused the 2009 H1N1 Pandemic was similar to the one that caused the 1918 Flu Pandemic. In spite of their virulence, these viruses did little harm to most people, who had certain antibodies or immunity. The same goes for the Covid-19 virus. If people can build immunity by producing antibodies through natural infection or vaccination, its virulence and pathogenicity will definitely decline.

The U.S. CDC has now changed its guidance to require mask-wearing indoors and in crowded places. That is a positive change and it’s based on science. We should also make some scientific changes and retain good measures, while doing our best to minimize the impact of the pandemic-related measures on people.

Countries around the world are striving to reopen. The Tokyo 2020 Summer Olympics was a first step. Many foreign athletes will come to China during the Beijing 2022 Winter Olympics. How should we deal with that?

Chen Yu: I think we can learn lessons from the pandemic-related measures taken at the Tokyo Olympics: when overseas personnel arrived in Japan, they went straight from the airport to the hotel for quarantine, and underwent three or four nucleic acid tests.

If the result is negative, and they are vaccinated and show no abnormal symptoms, do we still need to quarantine incoming personnel for 14 days? The judgement should be based on the result of Tokyo Olympics’ pandemic prevention, together with expert opinion.

Meanwhile, during the Winter Olympics, China will minimize people flows for better prevention and control of the pandemic.

As for exactly what should be done for the Winter Olympics, and how well pandemic prevention at the Tokyo Olympics has worked, I think national level public health organizations and infectious disease experts will formulate appropriate policies.

Chen Xiaoxue and Liu Chu are writers and editors at The Intellectuals, which is syndicated by Caixin.

Contact editor Flynn Murphy (

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