At present, the epidemic of New Coronary Pneumonia is spreading globally, and the number of infected people in the world has exceeded 2.68 million. For this new virus, countries are looking for different strategies to prevent and control. Following the UK ’s previous claim that mass immunization has received widespread attention, the latest research carried out in Germany and the United States has shown that the number of people infected in certain areas has far exceeded several or even tens of times previously. The first outbreak in Germany was infected With a rate of 15%, it was said that “realizing group immunization is not out of reach”, and suggested that some of the current prohibition measures implemented to prevent the spread of new coronaviruses should be ended. However, on April 19, German Chancellor Helger Braun made it clear that the German medical system cannot withstand the pressures caused by group immunization, so group immunization is not suitable for Germany.
What is mass immunity? Can it really let the virus disappear naturally by "doing nothing"? Our reporter interviewed Wu Zunyou, chief expert in epidemiology of the Chinese Center for Disease Control and Prevention.
To achieve mass immunity, 60% to 80% of people will be infected
Reporter: After the outbreak, some Western countries actually adopted a strategy of mass immunization. Is mass immunization feasible?
Wu Zunyou: The so-called group immunization strategy is to allow the vast majority of people to show immunity in the crowd and form an immune barrier at the social level. When one or more sources of infection enter such a social group, it will not cause an epidemic of infectious diseases.
In general, the method of achieving group immunization is mainly achieved through vaccination. The first serious infectious disease to be eliminated by humans, smallpox, is the widespread elimination of smallpox virus in human society through widespread vaccination worldwide. There are also many infectious diseases, which also reach a certain coverage through vaccination, form an immune barrier, achieve group immunity, and prevent its epidemic. For example, measles, polio, etc.
So far, humans have not developed a new coronavirus vaccine. In the absence of vaccination, to achieve group immunity, it can only be a natural infection.
The so-called group immunization strategy previously proposed by the United Kingdom is not to take active anti-epidemic measures, not to actively detect possible infected persons, not to track close contacts of patients, not to quarantine measures for close contacts, not to restrict the free activities of the people, and allow the virus The social population naturally spreads. When enough people are infected, there are enough people to develop immunity, and an immune barrier will be formed at the social level to resist the virus.
If this plan is implemented, 60% to 80% of people in the UK will be infected. This number is undoubtedly alarming, which will not only scare the local people, but also the world.
Using a negative strategy is unwilling to spend costs on preventing infection
Reporter: In your opinion, what logic was the British based on the strategy of group immunization?
Wu Zunyou: The British government originally planned to adopt this strategy, and there were theoretical foundations behind it. It is estimated that the introduction of this strategy has also been verified by some experts. By early March, humans already had some basic understanding of new coronary pneumonia.
First of all, the new coronavirus spreads particularly fast, and it is very difficult to prevent infection. Secondly, from the clinical characteristics, this new coronary pneumonia epidemic, there are more patients with mild disease, accounting for about 80%, they can be cured without treatment or symptomatic treatment. Like other infectious diseases, new coronary pneumonia also has some asymptomatic infections. In addition, the overall mortality rate of new coronary pneumonia is not high. If there is no basic disease such as hypertension, diabetes, cardiovascular disease, etc., the mortality rate of healthy people infected with new coronary pneumonia is about 1%.
The logic behind the strategy of mass immunization proposed by the United Kingdom at the time was that if the prevention and control could be liberalized and the epidemic could develop naturally, a large number of people would heal themselves and acquire immunity after natural infection. Then, concentrate medical efforts to treat critically ill patients in the crowd. That is to say, instead of spending on preventing "infection", work hard on preventing "death".
If this strategy can be effectively implemented, while the epidemic is under control, social vitality and economic development will not be damaged by strict control measures, which not only reduces the cost of fighting the epidemic, but also enables national health and economic and social development. Balance and maximize profits.
However, the implementation of the mass immunization strategy in the United Kingdom ended in less than two weeks.
Gambling of letting people be infected is appalling
Reporter: What is the reason for the halt of the group immunization strategy in the UK?
Wu Zunyou: The makers of the group immunization strategy initially ignored several issues. First, about 80% of mild patients, if they cannot get timely medical care, a considerable proportion of them may develop into severe or critically ill patients or even die.
Second, these patients who have developed from mild to severe or critically ill make the total number of patients in need of medical services much larger than originally expected to require medical care. In this way, there will be a "run-off" of medical services, causing the medical system to be paralyzed, and the case fatality rate is not only 1%. Crude fatality rates in neighbouring countries have shown that when medical services cannot meet the needs of patients, the fatality rate of patients will increase significantly.
To make a simple calculation, for the 60 million people in the UK, assuming 60% infection, 36 million people will be infected with the new coronavirus. If the mortality rate is 5%, then 1.8 million people will die. If a certain percentage of mild patients develop severe or critical illness, then the case fatality rate may climb to 10%, and there will be 3.6 million deaths.
Third, effective preventive measures (for example, not gathering, not getting together, wearing masks, keeping distance, washing hands frequently, etc.) are not special drugs, but they can still effectively block the spread of the new coronavirus and prevent people from getting infected. .
Fourth, when effective measures can be implemented, the government does not actively organize the implementation, watching the new crown virus spread among the crowd, watching the people raged by the virus and doing nothing, which is even more unacceptable on the ethical level.
For this reason, the UK had to terminate its so-called group immunization strategy. As Dr. Nicolas Noel, an immunologist at the Medical Teaching and Medical Center in Biseter, France, said: "When people are getting sicker and dying, this kind of gambling allows 60% of the population to be infected It is appalling. "
In addition to the United Kingdom, the Swedish government has also implemented a strategy of no detection, no isolation, no admission, and no announcement. But as of April 14, statistics show that the death rate of Sweden's new coronary pneumonia has reached 9%.
The most appropriate way to get immunized is through vaccination, which is optimistically expected to come out at the end of the year
Reporter: How does the human body get immune? What constitutes a population immune barrier?
Wu Zunyou: There are usually two ways for individuals to gain immunity to a certain virus. One is natural infection. After the virus is infected, the body's immune system produces antibodies to gain immunity. This method of gaining immunity is a natural selection process. Without treatment, or with the help of treatment, the infected person gets through and gets immunized. Another way is to artificially imitate natural infections, that is, to acquire acquired immunity through vaccination. The vaccine can be live attenuated vaccine, or dead virus vaccine, or genetically engineered vaccine.
Whether it is natural infection to obtain immunity or vaccination to obtain immunity, a certain percentage of people in the population need to be immunized, usually reaching 60% to 80% in order to play an immune barrier role.
The process of natural infection is not transferred by human will, but depends on the biological characteristics of the virus itself and the activity of the population. Obtaining immunity from natural infections is a natural process of uncontrolled development. Relying on natural infection to gain immunity to deal with the outbreak, to put it bluntly, there is no response, let the outbreak naturally rages.
To obtain immunity through vaccination is to quickly reach the population's immune barrier requirements in the shortest time by artificial means. This is a process of actively establishing an immune barrier, which is crucial for controlling the outbreak of new coronary pneumonia. In terms of technology, we still have to wait for the vaccine. It is optimistic to estimate that if everything goes well with the research, the vaccine is expected to come out by the end of the year.
But even after the vaccine came out, antibodies were produced through vaccination, it is not clear how long the immunity can be maintained, and whether the virus will mutate.
Even with antibodies does not mean once and for all
Reporter: Does it mean that it is safe for people who naturally develop antibodies and gain immunity after being infected with the virus?
Wu Zunyou: Regarding antibodies, some people may think that so many people have been infected with the virus and have antibodies, and our lives should be unimpeded without overprotection. This view ignores an important fact: even if someone has an antibody, so far, we do not know whether the antibody has a protective effect and how long it can be protected, not to mention that only a small number of people have antibodies.
Mike Ryan, the chief emergency expert of the World Health Organization, said that WHO is not sure whether the antibodies in the blood can fully prevent the re-infection of the new coronavirus. Even if the antibody is effective, there is no indication that a large number of people have produced antibodies, which can provide the so-called immune barrier to a larger population. Ryan said: "The large amount of preliminary information we have obtained shows that the proportion of seroconversion (ie, antibody production) in the population is quite low. Some people expect that most people may have produced antibodies, but the overall evidence is contrary.
Traditional public health protection measures are very important
Reporter: Under the current situation that the research on vaccines and antibodies is not clear, what prevention and control measures are effective?
Wu Zunyou: Before there was no preventive vaccine, traditional public health protection measures were the current effective measures to control the epidemic.
Current research on vaccines and antibodies is still in progress. Although the study concluded that there are more people actually infected with the new coronavirus in certain areas than originally thought, but that's all. Before conducting more research, do not rush to draw conclusions or change proven prevention and control policies.
At present, for an area, in the early stage of the epidemic, when there is no widespread spread at the social level, it is necessary to conduct a detailed epidemiological survey of each diagnosed patient as much as possible to determine all its close contacts Close contacts were observed for 14 days in isolation.
Quarantine observation of close contacts is very important to control the outbreak. Because some of the close contacts are already infected, these infected persons are already contagious two days before the clinical symptoms appear. If they are discovered before they become ill, it may have caused spread. Therefore, isolating close contacts is equivalent to removing high-risk people from the society and reducing the spread at the social level. This is a very important control measure.
Wearing a mask is another important measure to cut off the spread of the new coronavirus. Because the infected person is infectious two days before the symptoms appear, and the infected person in the incubation period is asymptomatic and unrecognizable, which can easily cause social transmission, especially in places with poor ventilation and people gathering. Therefore, always wear masks where people gather, such as public transportation.
If all the people actively respond to such measures as not gathering, not getting together, wearing masks, washing hands frequently, etc., in fact, a social immune barrier will naturally form at the social level. (Reporter Huang Hui)