At present, most scientists agree that in order to limit the spread of sars-cov-2, we need to take strict control measures, including effective contact tracking, detection and isolation, as well as maintaining social distance and wearing masks. Moreover, countries such as South Korea, China and New Zealand have successfully used this method to suppress the spread and spread of the virus. Some have even called for the clearance of covid-19 patients to try to eliminate the virus, rather than curb its spread. New Zealand seems to have succeeded in this regard, but after 100 days of no new cases, new infections have emerged, from international travel and other unknown sources. Although the above control measures can flatten the number of infected counties, it seems not feasible to achieve zero infection of covid-19.
For some island countries, it may be possible. In New Zealand, for example, it must prevent virus re-entry. Of course, this may require long-term and strict travel restrictions, as well as very strict nucleic acid testing of passengers before and after travel. Given that there is not much interest in extending border closures and that community-based control measures are not sufficient to eliminate the virus, zero infection seems unlikely at present, but it may be possible in the future if we use different methods.
The most effective way to inhibit covid-19 infection is to use the natural defense mechanism of human body, namely the immune system, to recover from the process of virus infection, which is usually related to the production of immunity. At present, researchers do not know whether sars-cov-2 can protect the body from being reinfected by the virus, but there are few cases of reinfection. Most of the infected people will produce antibodies against sars-cov-2, while some asymptomatic infected people may not produce antibodies, but the infection will still activate T cells of the immune system, thus providing an alternative defense mechanism. Therefore, it seems that the infection will generate immunity in most people, at least in the short term.
Understanding this mechanism, some scientists suggest that the virus should be allowed to spread in the population, so that the group immunity can be developed, and at the same time, the elderly and susceptible people should be protected, so that immunity can be generated in enough people, thus blocking the spread and spread of the disease. For highly transmitted viruses such as measles, the threshold of transmission is as high as 90% - 95%, Some people think that the threshold may be as low as 50% for sars-cov-2, and the consensus of experts is about 60% - 70%.
However, at present, the proportion of people infected with sars-cov-2 and recovered has not reached this level, and antibody research results also show that about 3% of people in Dublin have been infected with the virus, and the proportion in New York City may be higher, that is, 23%; however, the higher infection rate in New York City may lead to more deaths, even considering the large population; however, Sweden is under control On the other hand, a liberal policy has been adopted, resulting in more cases, and the death toll per million people is ten times that of neighboring Finland and Norway. In these places, the impact of the second wave may be lower, because a lot of people have been infected, but if the threshold of group immunity is not reached, the whole population still can not be protected. The consequence of trying to reach this threshold through natural infection may lead to more deaths of high-risk groups, including the elderly, obesity patients and patients with basic diseases In addition, some infected people will continue to develop long-term health complications, even if the initial infection is not very serious.
Therefore, for most people, the risks associated with pursuing group immunity make it an unacceptable strategy to suppress the virus, let alone eliminate it. Theoretically, however, vaccination may help us achieve the elusive zero infection situation. In many developed countries, the vaccine has reduced the incidence rate of diphtheria, tetanus and measles to near zero. At present, there are more than 200 kinds of sars-cov-2 vaccines under development, but if one vaccine can completely eliminate covid-19, the threshold may be a little high. Any vaccine needs to be very effective in preventing the disease and blocking the spread of the disease among people.
However, the fastest developing vaccine has turned its attention to a lower goal: to achieve at least 50% effectiveness, which is also the threshold for FDA approval. It may be an optimistic idea for scientists to develop an effective vaccine for the first time, and the vaccine needs to be effective for all ages and safe for all people Safety is the key, because any problems of any age group will affect other people's confidence and willingness to vaccinate. It will also take time to produce enough vaccine to vaccinate more than seven billion people around the world; for example, AstraZeneca, which is developing a new crown vaccine, has now reached an agreement to produce two billion doses by the end of 2021. The impact of covid-19 on humans may not be achieved overnight. The last natural case of smallpox occurred in 1977, 10 years after who launched the smallpox eradication program, and nearly 200 years after the development of the first smallpox vaccine, from the polio eradication initiative to poliomyelitis eradication in areas other than Pakistan and Afghanistan It also took nearly 30 years.
Therefore, although an effective vaccine can provide humans with the best chance of zero infection of covid-19, we should still be realistic about what may happen. Although it is not unimaginable to eliminate the virus in most parts of the world, it may take quite a long time.
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