Coronavirus: China’s cities are in a race for herd immunity – but what does that mean?

·7-min read

Several cities with advanced vaccination programmes are vying to become the first in China to reach herd immunity.

But questions remain about when exactly that tipping point – at which a population is largely protected from Covid-19 even though not everyone is immune – occurs. Experts say it cannot be calculated in a formula but rather must withstand the reality test.

The World Health Organization, which supports achieving herd immunity through vaccination rather than by allowing the disease to spread through the population, has said it cannot be achieved globally this year, partly because of limited vaccination in developing countries and the emergence of variants.

Do you have questions about the biggest topics and trends from around the world? Get the answers with SCMP Knowledge, our new platform of curated content with explainers, FAQs, analyses and infographics brought to you by our award-winning team.

By June 16, nearly 16 million people in Beijing – more than 80 per cent of its eligible population – had completed their vaccination regimen. In a total population of more than 22 million people, it equates to over 70 per cent of people in the capital being fully vaccinated. By Saturday, 18.3 million people had been vaccinated with at least one shot.

About 1.29 billion vaccine doses have been administered in China, according to the National Health Commission. Photo: Xinhua
About 1.29 billion vaccine doses have been administered in China, according to the National Health Commission. Photo: Xinhua

The level of vaccination in Beijing is similar to that of San Francisco which is on track to become the first city in the United States to reach herd immunity after vaccinating 74 per cent of those over 12 years old, the minimum eligible age for vaccination. In San Francisco 67 per cent of all residents had finished the complete vaccine regimen by Friday.

Chinese cities vulnerable to a higher risk of imported cases, those on the nation’s borders or the largest cities were deemed a priority and had broader access to vaccines, enabling more people to have jabs.

The southern island of Hainan had an early start to mass inoculation in March to “quickly build an immunity barrier” before two major events: the Boao Forum for Asia in April and the China International Consumer Products Expo in May. In the resort city of Sanya, which has a population of 1.03 million, more than 755,000 people, or 73 per cent of the total population, were fully inoculated by June 25.

In Shanghai, more than 16.8 million people – or over 67 per cent – of the city’s 25 million population had finished the full regimen by June 29.

It is followed by two other major cities: in Haikou 61 per cent of its residents had completed inoculation by June 21 while in Shenzhen 57 per cent of its total population of 17 million were fully vaccinated by June 26.

While these cities stood out with a high percentage of fully vaccinated people, the percentage is even higher when those who have had at least one shot are included. Strict social distancing and rules such as mask wearing, temperature taking and personal health code registration remain in place in these cities.

Vaccines and variants make Covid-19 herd immunity a moving target

Fan Fan was still wearing a mask while queuing with a friend to get into a downtown restaurant in Beijing last week even though it was hot and she had been vaccinated.

“Having worn masks for so many months, I am so used to it that it has become a habit. I feel strange without one in public now,” the 25-year-old office worker said.

On the way to the restaurant Fan took the subway, where she needed to have her temperature taken before being allowed to swipe her stored-value card. A security guard walked along the cars to ensure everyone had their mask properly fitted.

“Scanning a code to show my health code just takes seconds. Such inconveniences can’t be compared to catching Covid-19. To be honest I feel safe if everyone is wearing a mask in public,” Fan said.

Public health experts have repeatedly said China will need to maintain restrictions, such as strictly controlled national borders and social distancing rules, to prevent large outbreaks before the country achieves herd immunity. However, tests would be needed to confirm whether that level of protection was achieved, experts said.

Experts generally agree that at least 70 per cent of the population must be immune, through vaccination or past infection, to attain herd immunity. Because most Chinese cities have not had major outbreaks, they rely on accelerated vaccination programmes to achieve such protection.

With a changing degree of contagion emerging with coronavirus variants and an unknown level of protection from Chinese vaccines against spreading the pathogen, some public health experts, including respiratory specialist Zhong Nanshan and government-affiliated epidemiologist Shao Yiming, say China will need to vaccinate 80-85 per cent of the population to attain herd immunity.

What is driving China towards its coronavirus vaccination targets?

John Kaldor, a professor with the Kirby Institute at the University of New South Wales, said getting to herd immunity depended on many factors and even when achieved the protection might not be sustainable.

Vaccines can prevent some from symptomatic diseases but it is not clear how well the vaccines can prevent asymptomatic people passing on the virus.

“A country may reach the status of herd immunity today but lose it tomorrow due to these factors,” Kaldor said. “The probability of outbreaks is substantially reduced as coverage increases, but it does not diminish to zero. Current knowledge does not allow us to estimate the impact of these factors with a high degree of precision.”

The populations of large Chinese cities such as Shanghai were among those made a priority for vaccination. Photo: Reuters
The populations of large Chinese cities such as Shanghai were among those made a priority for vaccination. Photo: Reuters

Suzanne Judd, a professor at the University of Alabama’s school of public health, said that instead of “testing” for herd immunity, countries would need to monitor Covid-19 cases as an indicator after a certain percentage of vaccination was reached.

“We cannot measure herd immunity directly without a huge investment and diversion of resources towards testing rather than vaccination. Since that is not very cost effective, our best indicator is to look at case levels or vaccination rates,” Judd said. “After 70 per cent of the population have been vaccinated, cases should drop off to a level that we would consider ‘safe’. That will be the best way to track herd immunity in any country.”

With China largely shielded by strict testing and tough quarantine measures at the nation’s borders, mainland cities with high vaccination rates would have to open up first and see how well the population was protected, according to Kaldor.

“There will inevitably be a phase of trial and error as countries open up without knowing exactly how much their populations are protected,” he said. “This uncertainty underlines the value of comprehensive data collection and analysis to guide immediate public health responses.”

Anti-vaccine disinformation undermining Southeast Asia’s virus response

Beijing, which will host the Winter Olympics in February, remains largely closed. Some overseas flights have been directed to other cities first and high-level meetings have been convened as video conferences or hosted in other provinces.

The capital has scheduled a series of events, including the Asian Open Figure Skating Trophy from October 13 to 17 which serves as a test event for the Winter Olympics. The Second United Nations Global Sustainable Transport Conference, which was postponed from May last year has been rescheduled for mid-October.

An unidentified National Health Commission official in charge of disease prevention and control told mainland magazine Caijing last month that China was expected to inoculate 75 to 80 per cent of the total population by October, when some “local areas” can start gradually adjusting its epidemic control measures. Roughly 1.29 billion vaccine doses were given in China by July 3, according to the National Health Commission.

More from South China Morning Post:

This article Coronavirus: China’s cities are in a race for herd immunity – but what does that mean? first appeared on South China Morning Post

For the latest news from the South China Morning Post download our mobile app. Copyright 2021.

Our goal is to create a safe and engaging place for users to connect over interests and passions. In order to improve our community experience, we are temporarily suspending article commenting