Mar 14, 2020 07:07 PM

Opinion: ‘Quarantine’ and ‘Herd Immunity’ Strategies Both Full of Uncertainty

Photo: IC Photo
Photo: IC Photo

The spread of coronavirus is accelerating in the West, where cases in countries like Germany, the U.K. and the U.S. are surging. Judging from their current anti-virus measures, these countries seem to have adopted a strategy different from China’s. Rather than seeking to strictly contain the virus, they’ve resorted to slowing down the spread of the disease.

In Germany, Chancellor Angela Merkel said 70% of Germany's population could become infected. In the U.K, Prime Minister Boris Johnson said schools would stay open. He advised people with symptoms to stay at home for a week and advised senior citizens over the age of 70 to avoid certain activities.

In the U.S., the response policy has also been quite relaxed so far. Although a state of emergency was declared on March 13, there is yet to be strong policy support to get those suspected of having the virus effective testing.

China and Italy have adopted the strategy of shutting down cities and banning social activities, strictly isolating infected people. In China, that strategy came out of its experience fighting the severe acute respiratory syndrome (SARS) outbreak 17 years ago.

In the U.K., people involved in the government’s effort to fight the coronavirus have come up with a new strategy: “herd immunity.”

So how does the concept work?

Within a certain group of people, the circulation of diseases can be stopped after enough are infected and gain immunity. It is widely believed among infectious disease experts that if 67% of people in a group have immunity, a disease’s R0, or the number of people a sick person can infect, will drop below one. That will bring the disease under control.

In the early stage of the disease’s spread, strict control and isolation measures, such as city lockdown as adopted by Chinese government, will be very effective. China’s success in containing SARS had also proved that.

In public speech, British Prime Minister Johnson pointed out tight control and isolation strategies may not work any more, because the virus has passed the early stage and has already widely spread all around the world.

To some degree, Johnson’s offering of the “herd immunity” approach makes sense. First, the host of the virus is not clear, and the risk of transmission is still there; second, many people may already have contracted the virus but has not showed any symptoms. They could infect others at the right time; third, in an era of globalization, it is not possible to entirely close a country to the outside world – people infected overseas will bring the disease back to the country. So the need to build up a herd immunity is necessary.

Within a society, if herd immunity is not built up, the virus will continue to spread, and infectious diseases are very difficult to control. Given the current situation in China, the epidemic is indeed being under control, but outbreaks could happen again after restriction measures are lifted, as the virus already exists. It is impossible for a society to be quarantined all the time.

How do we build up a herd immunity? There are two ways: one is through exposure, and the other is with a vaccine. Since there is as yet no vaccine, there is only one way: creating the conditions for exposure, either actively or passively.

The overall mortality rate of the coronavirus stands at less than 1%, with the majority of deaths being elderly people and those with underlying diseases. We have to face the hard reality that the virus only accelerates the process of their death.

German Chancellor Angela Merkel has been saying that at least 70% of the German population could eventually be infected. Only when 70% of people are infected will herd immunity be achieved.

The British and German governments have adopted a more laissez-faire approach which involves three steps: first, encourage young people to get infected first, while protecting the elderly by keeping them at home. Second, adopt some social distancing measures, including closing schools, canceling some large-scale activities, to prolong the infection cycle of the virus and prevent it from spreading too fast and overwhelming hospitals. Finally, herd immunity will be achieved, and the vulnerable will be safe.

The approach is extraordinarily risky. Many of the characteristics of the novel coronavirus are still unknown.

First, will the lethality of the virus to young people always stay low? Many of the dead in Wuhan have been young people. The well-known whistleblower doctor Li Wenliang died from the disease at 34 years old.

Third, the coronavirus is a kind of a RNA virus, which can mutate. There is yet to be scientific research on whether acquired immunity is effective against the mutated virus and how long it can last.

Fourth, the death rate of the coronavirus in Italy now stands at more than 6%, while in China it is 4%. Even if the death rate in Germany was just 0.2%, if 70% of the total population of 83 million gets infected, it will take more than 100,000 lives. That’s before getting into how recovered patients may experience long term side-effects. Can a society afford such a price?

After the large-scale spread of the virus, the population within a society will ultimately form herd immunity, either by natural exposure or through a vaccine. A society can not run normally with tightly-controlled epidemic measures in place.

China has adopted a different strategy and has contained the epidemic through strict social control and isolation. However, the population in China is yet to build up herd immunity.

Hopefully, a vaccine will be available soon. But before one is available, if we relax our tight controls, the virus will be likely be revived.

Though the cost of both these epidemic response strategies is varied, one thing is true of both: they are full of uncertainty.

Yu Xiaohua is a Professor of Agricultural Economics in Developing and Transition Countries at the University of Göttingen, Germany.

Translated by Mo Yelin.

Contact editor Flynn Murphy (

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