If the fight against the spread of the new crown pneumonia epidemic is a global battle, the "herd immunity" strategy recently thrown out by the British government has been regarded by medical experts in various countries as "brightening the flag directly to the virus", but some people have argued that "this approach was It worked. " What kind of medical concept is "herd immunity"? Does it really "match" this new crown epidemic?

Herd immunity has a strict scope

The first to throw out the "herd immunity" theory was Patrick Valence, chief scientific adviser of the United Kingdom. In an interview with British Sky Television on the 13th, Patrick said that about 60% of Britons will be infected with the new crown virus in order to make society "herd immunity" to future outbreaks. There are currently about 66 million people in Britain. According to Patrick's prediction, 40 million people are infected with the new crown virus.

The British government made this decision because it determined that the "containment" phase of the country's epidemic had failed, and it had entered the "delayed" phase. The outbreak was inevitable. In order to delay the high incidence of New Coronary Pneumonia from April in the traditional flu season to summer to ease the pressure on the hospital, the British government decided to tolerate the slow development of the epidemic, expecting that most people will be asymptomatic or have only mild symptoms after the occult infection, Thereby gaining universal immunity in the population to control the outbreak.

The concept of "herd immunity" is widely used in the prevention and control of infectious diseases. According to a report published by the University of Oxford, "herd immunity" is only applicable to infectious diseases and not effective for non-communicable diseases. At the core of "herd immunity" is the need for enough people to be immune.

According to an article published by Yu Xiaohua, Chair Professor of the Department of Agricultural Economics and Rural Development at the University of Göttingen in Germany, whether "herd immunity" is effective requires the threshold of "herd immunity", which is related to the basic R0 value of the virus (ie, one on average). The number of patients infected, R0 <1 means that the infectious disease is under control). Papers published by scholars from many countries show that the academic community generally believes that the R0 value of the new coronavirus is about 2-3, which means that in order to form "herd immunity" in the United Kingdom, 50% to 67% of people need to be immune to the new coronavirus.

There are many successful cases of using "herd immunity" to successfully control epidemics. Historically, the small infectious disease smallpox that was eliminated by humans relied on the principle of "herd immunity". According to data released by WHO, it has plagued humans for at least 3,000 years before it was wiped out, killing 300 million people in the 20th century alone, and the last known case of smallpox epidemics was reported in Somalia in 1977. With the worldwide spread of the vaccine, WHO announced the elimination of smallpox in 1980. Historically, people have also used the principle of "herd immunity" to control the spread of diseases such as measles and rinderpest through vaccination.

But the University of Oxford emphasised that "herd immunity" is effective only if most people have been vaccinated. For example, 19 out of 20 people need a measles vaccine to protect unvaccinated people. If people are not vaccinated, herd immunity will fail. In 2000, the United Nations announced that the United States had eliminated measles. However, in 2019, the overall outbreak of measles in the United States was mainly due to the decrease in the number of people who received the measles vaccine and the "herd immunity" failed.

An unnamed domestic epidemiologist told the Global Times reporter on the 15th that the "herd immunity" theory itself is not a problem, but only if a vaccine has been developed. This time in the United Kingdom, before the research and development of the new crown virus vaccine has been completed, this passive "herd immunity" strategy is adopted, which is reminiscent of the history of British parents who took their children to the home of children with chickenpox to get their children immune force.

An article published by Rao Yi, the president of Capital Medical University, on the 14th said that "herd immunity" is completely a "lie" of the British Prime Minister. Rao Yi said that, in general, if a few people refuse to be vaccinated, but most people gain immunity after being vaccinated, the virus may not reach people who have not been vaccinated, causing the chain of transmission to be interrupted and a "herd immunity phenomenon". However, in the case of a new virus, no vaccine, and very few people may have innate immunity, it is impossible to "group immunity" without curbing the spread of the virus and exposing the entire population to the virus. Relying on only a few naturally resistant people, it is impossible to stop the spread of the virus in the population like those who have been vaccinated to gain immunity. He criticized the move as a complete denial of basic human medical progress, and if so, "should we give up all vaccine efforts?" ▲

There are too many uncertainties in the new crown epidemic

WHO spokesman Margaret Harris on the 14th questioned Britain's use of a "herd immunity" strategy to combat the new crown virus. She made it clear that New Coronavirus has not existed in humans for a long time, and that the current knowledge of New Coronavirus in science is not enough, so it does not know its role in immunology.

The main reason for Patrick ’s and British health officials ’judgement is that“ most people with new coronavirus infection have relatively mild symptoms ”. The guidance issued by the UK ’s Ministry of Public Health also emphasizes that the UK will not New patients were tested for new coronavirus.

However, this basis of judgment has been heavily questioned. On the 14th, Ning Yi, a professor at the Peking University Meinian Institute of Public Health, believed that Patrick's assumption was wrong. Ning Yi commented, "This is a strategy of 'seeing death as if it is home', and it is also impractical."

According to Rao Yi, although there are asymptomatic patients with a new crown virus infection and a large number of mild patients, both mild patients and asymptomatic infections have been proven to be able to transmit to others, and they have not formed a "natural barrier". The so-called "natural barrier" means that not only do they have no symptoms or mild symptoms, but they do not spread to others. The truth is, they are contagious.

Although according to the data released by the China Centers for Disease Control and Prevention, the proportion of mild cases of new crown pneumonia is about 80%, but experts from the Beijing Aid E Medical Team told the Global Times that the condition of the new crown virus changes rapidly. Timely treatment will greatly increase the severity and mortality. At present, the mortality rate of New Coronary Pneumonia in China is 3.9%, which is much higher than that of viral influenza. If the UK does not adopt compulsory isolation measures and let the infection go, it will probably see a higher mortality rate than 3.9%.

In addition, when the vaccine is used to obtain "herd immunity", the safety of the vaccine has been verified layer by layer, and the probability of adverse reactions is very small. Even so, there was a 30-minute waiting period after the vaccine was given. However, such a means of protection for mildly infected persons does not exist in the "herd immunization" strategy proposed by the British government. It is currently known that a considerable number of people with new coronavirus infection will develop severe or even critical illness, and medical personnel need to closely monitor the course of the disease. In the UK, mild patients are required to be isolated at home by themselves. Once the illness worsens, how to ensure that they can be treated in time? Can mild patients gain immunity after recovery?

Former WHO Director of Maternal, Child and Adolescent Health Anthony Costello said on the 14th that "herd immunity" in the UK may not last. If the new crown virus is like the flu, new vaccines will need to be developed every year. For strains, the effect of "herd immunity" is limited. ▲

The UK move could have serious consequences

Regarding the consequences of the British "herd immunization" strategy, hundreds of scientists from the scientific community issued an open letter to the British government on the 14th, stating that "seeking" herd immunization "at this juncture does not seem to be a viable option. More pressure and more people taking unnecessary risks. "WHO Director-General Tan Desai also said that the new crown epidemic is controllable. Those countries that have decided to abandon the use of basic public health measures to prevent and control may eventually face bigger problems that will place a heavier burden on the health system and now need to take tougher measures to control it. Former WHO Director of Child and Adolescent Health Anthony Costello said on the 14th that the United Kingdom ’s strategy to seek “herd immunity” is out of touch with other countries, which may conflict with WHO ’s strategy. The organization's policy is to curb the spread of the virus by tracking all cases.

Yuan Guoyong, chair professor of the Department of Microbiology at the University of Hong Kong, said on the 15th that the "herd immunity" strategy is usually used when the disease mortality rate is very low, but the epidemic mortality rate is between 1% and 3%. People or chronically ill patients must be hospitalized. The emergency room, ward, and even the ICU will all be "full", which may paralyze the medical system. In addition, this may also infect doctors and nurses, and even lead to the death of medical staff, which will cause great panic.

As Yuan Guoyong said, the British government's plan requires the new crown to keep the mortality rate as low as possible. "The government does not seem to be following a strategy to prevent and control the flu, let alone not the flu this time. The situation with the new crown virus is much worse," said Devi Sridhar, chairman of the University of Edinburgh's global public health, on social media on the 14th. And the health impact is staggering. "

In addition, the British "herd immunity" strategy will bring serious consequences including ethics. Rao Yi questioned that relying on the formation of "herd immunity" after the first round of infection was at the cost of giving up the part of the people who were infected in the first round. If the coronavirus mutates every year like the flu, do you have to give up the same percentage of people every time? If 1% of the country's population died this time to obtain "herd immunity", then why next time protect the susceptible to other diseases? Without protection, what is the bottom line of human civilization?

Professor Zhang Wenhong, director of the Department of Infectious Diseases, Huashan Hospital affiliated to Fudan University, said on the 15th that from the perspective of the current widespread acceptance of the widespread spread of the new crown virus, the subsequent development of the new crown disease is not optimistic. China, poses a greater threat to regions with less developed medical resources.

The latest research released by American scholars shows that if Italy acts early, it is still possible to control the spread of the epidemic, but it is too late for them to respond. As for the British government's decision, an Italian wrote on social media: "Every day of delay will bring a lot of death and economic loss. This is an experience from Italy." ▲