Can COVID-19 be eradicated like smallpox?

On August 20 and 21, 2021, five newly confirmed cases related to Pudong Airport were reported in Shanghai.

Although the momentum of the epidemic was quickly extinguished, it still strained the nerves of people who had just recovered from the Nanjing Yangzhou epidemic.

In the face of the still existing epidemic threat, how should we continue to respond? What factors are the core issues that we focus on in epidemic prevention and control?    Will the novel coronavirus be eradicated like smallpox? In fact, the discussion on epidemic prevention and control has continued since the beginning of 2020.

When we talk about epidemic prevention and control, what are we talking about? After more than a year of fighting with COVID-19, we tried again to answer this question.

  We first assume two most extreme possibilities: human complete eradication of the virus vs human abandonment of all resistance.

Then connect the two most extreme possibilities to form this coordinate axis, which can be understood as the different epidemic prevention intensity taken by human beings in the face of epidemic situation.

  What kind of anchor point should we choose on this coordinate? It is easier to discuss the left and right endpoints, which are the two most extreme possibilities we have assumed.

  The first extreme that can be excluded is “giving up all resistance”.

  Although at the beginning of the epidemic, some countries or regions tried to achieve mass immunization through natural infection, in fact, in the face of rapidly increasing cases, most countries have more or less implemented some epidemic prevention and control measures.

  Recently, the new delta mutant has brought new variables.

  According to a CDC document exposed by the Washington Post, the basic infection number (R0) of delta mutant is about 5 ~ 9.5, which is comparable to chickenpox (about 8 ~ 9) in infectious diseases, second only to measles (about 15).

  Source: reference 2.

That is to say, if we do not interfere effectively with the prevalence of COVID-19 strain Delta, the average Delta infected person will spread the virus to 5~8 close contacts who have no immunity to the virus.

In contrast, the R0 of the original strain of novel coronavirus previously evaluated by CDC was 2, which was equivalent to the common cold.

  If you want to eliminate infectious diseases through mass immunization, the immunization rate of the population needs to be 1-1 / R0.

According to CDC evaluation, R0 is about 5 ~ 9.5, and the population immunization rate needs to reach nearly 90%.

  Let’s start with eradication.

  Reviewing the history of human response to the virus, the most successful battle is the eradication of smallpox.

In 1977, Somalia reported the last case of smallpox infection.

In 1980, who officially announced the eradication of smallpox worldwide.

  Is it possible for COVID-19 to disappear from the world like smallpox?   Li Dong, deputy chief physician of the General Department of infection department of Beijing You’an Hospital Affiliated to Capital Medical University, once believed that at present, the possibility of human eradicating the novel coronavirus is almost zero.

” Compared with smallpox, the novel coronavirus is not so threatening.

It is difficult for the world to unite and deal with the novel coronavirus with the determination to deal with smallpox.

”   The reason why smallpox can be completely eradicated, in addition to the effective intervention of smallpox vaccine, also depends on people’s timely detection of signs of infection and epidemic situation, and that smallpox virus only infects people and has no natural host and animal vector in nature.

But at the moment, it seems that it is difficult for COVID-19 to succeed.

  Li Dongceng told Ding Xiang Yuan that a major difficulty in eradicating the novel coronavirus was the emergence of a large number of asymptomatic and mild infectious patients in COVID-19.

  The latest research paper of PNAs systematically reviewed more than 350 studies.

The data showed that 35.1% of the novel coronavirus infected people did not show any symptoms in the whole course of the disease, that is, more than 1 / 3 of the infected people were asymptomatic, but they also had the ability to transmit the virus.

  Figure source: Reference 1 “a large number of asymptomatic infected people make it difficult to find the signs of the epidemic at the first time, and it is difficult for the infected people to be isolated at one time.

On this basis, it is difficult for us to discuss the possibility of eradicating the novel coronavirus.” Li dongzeng said.

  Zhang Hongtao, an associate professor at Pennsylvania Medical College, mentioned another feature of COVID-19, which is more than human infection.

  Recently, a paper by the National Wildlife Research Center showed that 152 of the 385 white tailed deer samples collected in 2021 detected novel coronavirus antibodies, accounting for 39% of the total samples.

Previously, other countries and regions have also successively reported cases of novel coronaviruss infected by tigers, snow leopards, Asian lions and other animals.

  According to Zhang Hongtao, from the existing evidence, COVID-19 is likely to infect humans and spread among animal.

” Even if the virus is extinct in human society, it may still exist in other animals in nature.

If we want to eradicate the novel coronavirus, we need to consider animal vaccines and other means, which are very costly and difficult.

”    How to understand the vaccine under breakthrough infection? Let’s look at the axis drawn at the beginning again.

When we basically give up the illusion of two extreme situations, the discussion on epidemic prevention and control becomes the discussion on the intensity of prevention and control – what anchor point should we choose on this coordinate axis? What factors will play a crucial role in our choice? First, it is the characteristics of the virus itself and the existing medical countermeasures.

At the beginning of 2021, delta mutant suddenly emerged, quickly gained the upper hand in the pandemic, and caused local and small-scale epidemics in China for many times.

On August 20 and 21, Shanghai announced the details of five confirmed cases related to Pudong Airport, and all five patients were vaccinated with Xinguan vaccine.

Facing the continuous threat of virus, how should we understand the role of vaccine? Li Dong once told Ding Xiangyuan that it is impossible to completely control the epidemic situation through vaccines worldwide.

” First, we have seen the ability of mutant strains to escape immunity, which may discount the effect of the vaccine; Second, the global vaccine resources are unequal, and the vaccination time cannot be unified.

There will always be epidemic situations in some parts of the world.

At present, the protection period of the vaccine is not so long, and there is likely to be repeated infection after the protection period.

” Zhang Hongtao believes that at present, some expectations for vaccines may be “too high” Vaccines can help humans cope with the virus, but we can not regard it as the only weapon.

In addition to vaccines, we have many other epidemic prevention measures that must be coordinated to achieve the goal of controlling the epidemic as soon as possible.

” On August 18, the U.S.

government announced that it is expected to open enhanced vaccination from September 20 this year.

But just a month ago, the who just issued the most severe criticism on booster needles, pointing out that in countries and regions where vaccines should be provided to many countries and regions lacking vaccines, pharmaceutical enterprises peddle booster needles to developed countries that do not lack vaccines out of “greed” The vaccine has been approved for more than half a year, but now the global vaccination coverage is far from enough.

” Zhang Hongtao believes that an important problem of vaccines at this stage is production capacity.

” For mutant strains, the vaccine needs to focus on whether the research and development speed can keep up with the speed of virus renewal, which is also a difficult problem.

” Li Dong once said that the most important role of the novel coronavirus vaccine at this stage is to prevent the severe disease rate, hospitalization rate and mortality.

” If we put the goal of the vaccine on the prevention of severe disease rate, hospitalization rate and mortality, then the role of the vaccine may be more targeted by strengthening the needle for the elderly, people with basic diseases and other severe and high-risk people..