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Ready to Coexist with New Coronavirus nCOVD? | Mass Immunization Theory


Mass immunization may be the inevitable result: are we ready to coexist with the new coronavirus nCOVD?

After Patrick Valence, the UK’s chief scientific adviser, first proposed the concept of “group immunization” on March 13, experts and media criticized a popular pessimism argument that if effective vaccines have not After birth, in the next 1 to 2 years, "group immunization" is an inevitable result of passive formation even if it is not a actively selected strategy.

On April 5, some public places in London, England were closed to reduce people's gathering activities.

In the first week of April, the world did not get better

On the evening of April 5, British Prime Minister Boris Johnson spent the first weekend of the month in the hospital, ten days after his diagnosis. His doctor described it as a "preventive measure", although Boris has shown persistent fever. But on Monday afternoon a few hours later, his condition began to deteriorate, and he has now been transferred to the intensive care unit of the hospital, where Foreign Minister Dominique Rab is temporarily acting as prime minister.

On April 4, Graham Medley, a professor of epidemiological models at Imperial College London and a senior adviser to the Johnson administration, suggested that the UK should reconsider whether to adopt a "group immunization" policy. He said: "The only viable way to help us through this emergency health event is to make people infected and therefore no longer vulnerable."

He warned that the "blockade" policy that the UK is adopting has "driven the whole country to the corner". If this continues, it will have a more serious negative impact than the new crown virus-the economy will fall into a total collapse. In his view, the blockade only won some time and prevented the short-term spread, but did not solve any problems. Medley pointed out that on April 13, the Prime Minister will make a "major decision" to determine whether the blockade policy will continue.

After Patrick Valence, the UK ’s chief scientific adviser, first proposed the concept of “group immunization” on March 13, experts and media criticized a popular pessimism argument that if effective vaccines have not After birth, in the next 1 to 2 years, "group immunization" is an inevitable result of passive formation even if it is not a actively selected strategy.

A recent study published by the University of Oxford in the UK seems to have advanced this result. After the model deduction, the researchers concluded that as of March 19, 36% to 68% of the people in the United Kingdom may have been infected with the new corona virus; Italy may have 60% to 80% of the people infected with the new corona virus by March 6 . This means that Britain and Italy may have formed a practical "group immunization".

This is just a model-based speculation, which needs to be confirmed by more accurate testing. However, if countries such as Europe and the United States will achieve "group immunization" in the future, for countries such as China that have adopted strict control measures, because most people are not infected and lack immunity, a "vaccination gap" will be formed, which is a very dangerous signal of.

(Profile picture) British Prime Minister Boris Johnson. Ten days after the diagnosis of new coronary pneumonia, Boris Johnson was transferred to the intensive care unit on the evening of April 6 due to worsening of his condition. Figure / IC

Coronavirus across countries and the UK

68% of Britons are already infected is the most extreme result

On March 24th, the Oxford University Infectious Disease Evolutionary Ecology team published a study that used the new crown death case data reported by the United Kingdom and Italy to simulate three different scenarios by giving different parameters to derive the possibility of the United Kingdom and Italy. The actual number of people who have been infected with the new coronavirus.

In the first two simulation scenarios, the setting of "the proportion of high-risk susceptible people in the crowd" is the same, which is 1%, that is, one out of 100 people is an elderly person over 65 or has a serious underlying disease, or breathing after infection Patients with serious complications such as failure. But in the first scenario, the basic infection number (R0) is set to 2.25, that is, an infected person can infect 2.25 people. It is estimated that as of March 19, at least 36% of the British people have been infected with the new crown virus. In the second scenario, the R0 value was increased to 2.75. In the model, the proportion of British people infected with the new coronavirus also increased to 40%.

The third scenario sets the high-risk susceptible population to 0.1%. According to the model, death cases are a small part of the high-risk susceptible population, so given the number of deaths, the lower the proportion of the high-risk susceptible population in the population, the greater the base of infection of the population. In this case, even if the smaller R0 value of 2.25 is used for calculation, at least 68% of the British people are already infected. In this regard, Paul Kellerman, one of the researchers and a professor of virology at Oxford University, said: "68% of British people have been infected is the most extreme result."

Corona virus in Italy

The same is true in Italy. According to the above three different parameter settings, it can be concluded that as of March 6th, 60% to 80% of the people in Italy may be infected with the new crown virus.

To verify the accuracy of the model, the researchers simulated the cumulative number of deaths in the UK and Italy within 15 days after the first death case. The results found that the results of the three scenarios were very consistent with the increase in the cumulative death case data for both countries. Therefore, the study points out that Britain and Italy may have accumulated sufficient levels of group immunity.

More than half of the people in the UK have been infected with the new crown nCOVD?

But Simon Gerbins, professor of infectious biology at the Bright Laboratory in the United Kingdom, pointed out that this does not mean that more than half of the people in the UK have been infected with the new crown. The third most extreme scenario is based on the high-risk susceptible The assumption is only 0.1% above the assumption. Once this number becomes 1%, the number of infections has dropped a lot, only 36% - 40%. "But the point is that no one knows what the proportion of high-risk people is."

According to Paul Hunt, a professor of pharmacy at East Anglia University, it is too early to make such an assumption. This ratio is related to the age distribution of the population, the proportion of people with basic diseases and the closeness of social connections in a society, and these will continue to change with the development of the epidemic.

A recent report published by the Kaiser Family Foundation, a nonprofit research organization that has long been concerned about public health policies, pointed out that in the United States, about 37.6% of adults over the age of 18 will experience serious symptoms after being infected with the new coronavirus. This is equivalent to 4 out of 10 people belonging to high-risk susceptible groups. 
In addition, this ratio is different in different states. It can reach 49.3% in the highest state of West Virginia and 30% in the lowest state of Utah. The study defines high-risk susceptible populations as: elderly people over 65 years old, and people between 18 and 64 years old with heart disease, chronic obstructive pulmonary disease, uncontrollable asthma or diabetes. The above figures are very different from the parameters set in the paper.

The setting of R0 also faces the same question. The WHO believes that the basic infection number of the new coronavirus is 1.4 to 2.5, and the median is 1.95. But the latest report, which combines 12 related studies, shows that the more appropriate R0 should be 3.28, with a median of 2.79. 
Throughout March, with the rapid spread of the epidemic in continental Europe, the Imperial College ’s epidemiology team raised their estimates of R0 twice, the first time on March 26, setting the range of R0 values. It was set at 2.4 ~ 3.3, and after four days, it was increased to 3 - 4.7 again.

In addition to the problem of parameter setting, the biggest problem of this model in the view of Gerbins is the assumption that the United Kingdom and Italy are an absolutely homogeneous population settlement, that is, different groups in different regions can be exposed to the virus absolutely equally. And infect others.

Chinese Center for Disease Control and Prevention on nCOVD

Zeng Guang, the chief epidemiologist of the Chinese Center for Disease Control and Prevention, told that the population is very complex and unbalanced. For example, within Italy, the differences in infections between different regions are very different. Hunt also pointed out that the ability of asymptomatic, mild and severe patients to transmit the virus to others is different. This model does not take into account these differences. "This will cause an overestimation of the virus infection rate, which will affect the estimation of the actual infected population."

Giuseppe Remuzi, a well-known professor of nephrology in Italy, pointed out that it is impossible for more than 60% of people in Italy to be infected, unless it is in some specific areas, such as Bergamo, a severely affected area. Only large-scale serum testing studies can provide more reliable estimates.

The usefulness of such models is that after deducing the corresponding number of deaths and infection rates, on the one hand, it promotes the government to introduce a more active public health policy. On the other hand, after the end of the epidemic prevention and control, the actual data The comparison is an assessment of the effectiveness of the policy.

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