"Herd Immunity of COVID-19" won't be achieved in a lifetime?!

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“Herd Immunity of COVID-19” won’t be achieved in a lifetime?!

“Herd Immunity of COVID-19” won’t be achieved in a lifetime?! “Don’t talk about herd immunity anymore, it won’t be achieved in a lifetime”

“When discussing the new coronavirus, stop mentioning ‘herd immunity’. In our lifetime, it will not be achieved-or is unlikely to be achieved.” On August 4, local time, the director of Infectious Disease Analysis and Research of South African Medical Research Council , Professor Shabir Madi of University of the Witwatersrand, Johannesburg wrote an article.

Information from the World Health Organization (WHO) shows that “herd immunity”, also known as “crowd immunity”, is an indirect protection against infectious diseases. This protection is formed when people become immune through vaccinations or previous illnesses.

Shabir Madi said that the current spread of the concept of “herd immunity” will cause a misunderstanding that we can enter the stage of complete elimination of the virus. That means that in the absence of other interventions (such as wearing masks), the chain of transmission of the virus in the population may also be interrupted. “But this is unlikely to happen anymore.”

Over time, the protective efficacy of the vaccine has declined, and more powerful variants have appeared. A higher proportion of people are skeptical of the vaccine, hesitate in vaccination, and breakthrough infections continue to appear… More and more facts show that even in local areas Within the scope, it is also difficult for humans to completely eliminate the new coronavirus, or it may need to coexist with it for a long time or even permanently.

Our opponent is stronger

As early as March this year, “Nature” wrote an article stating that “herd immunity” may be difficult to achieve. The primary reason lies in the “protective efficacy of vaccines.”

In the spring of 2021, the United States, the United Kingdom, Israel, etc. rapidly promoted vaccination, and the epidemic curve was gradually flattened. This has strengthened the confidence in “to popularize vaccines and restore normalcy.” The United States therefore proposed that on July 4 this year, 70% of adults will have at least one dose of the vaccine and will be fully unblocked.

Until August 2, local time, the United States initially reached the goal of one-dose vaccination for adults, and the two-dose vaccination rate of the total population reached 49.7%. However, the core indicators of the country’s epidemic have risen instead of falling. As of July 30, the average number of newly diagnosed cases, average death cases (300), and hospitalization cases in the United States on the 7th increased by 64.1%, 33.3%, and 46.3% respectively from the previous week. The US Centers for Disease Control and Prevention (CDC) made a recommendation: put on the mask you removed.

In Israel, about 62% of the 9.3 million population have received at least one dose of the vaccine, and about 56% have completed two doses of the vaccine. However, after the relaxation of epidemic prevention measures, the country’s epidemic has rebounded. On June 22, Prime Minister Bennett stated that the epidemic had re-erupted.

Part of the reason is that over time, the level of antibodies in the vaccinated person decreases. Studies have shown that 6 months after the full course of immunization, the levels of neutralizing antibodies for people aged 18-59 and people over 60 will decrease by 28.6%-91.9%. This does not mean that vaccine protection does not exist. To what level it drops and its protective power will disappear, further research is needed.

But it is the mutant strain Delta that really delays the pace of unblocking the United States. At present, 132 countries and regions around the world have reported cases of infection with this strain. More than 90% of infections in the United States originate from this strain.

Studies have shown that Delta’s “fierceness” stems from mutations in important positions of the viral spike protein. For example, mutations in the two positions of T478K and L452R change the structure of the spike protein, making it easier to bind to receptors on the surface of human cells, easier to replicate and spread in the human body, and easier to escape the recognition of the human immune system. .

This means that even if vaccinated, people may still have a “breakthrough infection.” According to a report by the ABC on July 31, the two major hospitals in San Francisco-San Francisco General Hospital (SFGH) and University of California San Francisco (UCSF) Medical Center-have reported a total of 230 medical staff infected with the disease, most of which are breakthrough cases .

According to the current incidence rate in the CDC internal documents of the United States, among the 162 million vaccinated people in the United States, there will be 35,000 symptomatic infections every week. The CDC said that compared with those who have not been vaccinated, the risk of infection among those who have been vaccinated is widening. For example, the risk of morbidity will be reduced by 87.5%, and the risk of hospitalization and death will be reduced by 96%. It can be seen that even if there is a breakthrough infection, it may not cause a run on medical resources.

But the negative thing is that there is no difference between the viral load of the vaccinated people and the unvaccinated people, and the chain of virus transmission cannot be cut off. In July, a local epidemic occurred in Barnstable County, Massachusetts, and a total of 469 cases of COVID-19 infection were reported. Among them, 346 patients completed two doses of vaccination (74%). The US CDC said that due to testing bias, or there are more asymptomatic infections that have not been detected.

Mild and asymptomatic transmission is precisely a major feature of the spread of the new coronavirus. Based on studies from various countries, up to 80% of people infected with the new coronavirus have no obvious clinical symptoms, but have the ability to infect others. US CDC data shows that as many as 59% of new cases may be transmitted by asymptomatic people.

This transmission situation is also reflected in this round of domestic epidemics in some countries. As of 18:00 on August 5, Zhengzhou City, Henan Province had reported a total of 112 cases of local infections, of which 93 cases were asymptomatic infections.

“If the vaccine cannot completely block transmission and strengthen the concept of ‘herd immunity’, it may weaken people’s confidence in the vaccine and doubt the benefits of vaccination,” said Shabir Madi.

New mutant strain, new “herd immunity” threshold

“The intellectual frontier scholar” and Zhejiang University professor Wang Liming wrote in the article “Delta Mutant Invasion, COVID-19 Prevention and Control Needs New Ideas”: “We must face up to such a long-term result: With the continuous increase in the number of virus infections, the virus The gene sequence can continue to mutate, and new virus variants will continue to appear. Even in the future, new virus strains that are more transmissible, more pathogenic, and better able to escape vaccine protection than the delta mutant will appear.”

New threats have emerged.

On July 19, the Methodist Hospital in Houston, Texas, USA, reported the first case of infection with the mutant strain “lambda”. On August 4, the United States reported 1053 cases of infection with related strains.

The Lambda mutant strain first appeared in Peru in August 2020. According to Peru’s official statistics, since April 2021, 81% of the country’s newly confirmed cases have been lambda infections. In neighboring Chile, the detection rate of Lambda accounts for 1/3 of the new cases. At the same time, the number of infections in Chile has increased rapidly, and even if the vaccination rate reaches 69%, the growth curve has not been flattened.

This may be related to the “founder effect”. That is, the mutant strain became popular in a densely populated and geographically restricted area, and became the main epidemic strain over time.

On the other hand, it may also be due to its “super transmission” nature. The University of Tokyo in Japan recently released a pre-printed study, claiming that the lambda strain has three major site mutations, which can resist vaccine-induced neutralizing antibodies and enhance immune escape ability. At the same time, it has T76I and L452Q mutations and is highly infectious. Some media describe that these two characteristics may make Lambda surpass Delta and become the new “drug king.”

Changes in the spread of the virus will lead to changes in the basic number of infections (R0), thereby affecting the compliance value of “herd immunity”. “The Lancet” issued an article in February that if the COVID-19 virus’s R0 in the Amazon area is calculated at 2.5-3.0, the cumulative proportion of the infected population required to achieve “herd immunity” is 60%-67%.

According to US CDC data, the R0 value of the Delta strain rose to 5-9. That is, among people without immunity, a delta virus carrier can infect 5-9 people, which is almost the same as the spread of chickenpox.

At the press conference on epidemic prevention and control held in Guangzhou on May 31, Zheng Huizhen, chief expert on disease control of the Guangdong Preventive Medicine Association, stated that the estimated data (R0) of the epidemic in Guangzhou reached 6.06. For example, she said, if R0 is 3, about 67% of people in the population are immune to build an immune barrier; if R0 is 6, it needs nearly 85% of people to have immunity.

According to China seventh national census data released in May 2021, the population of 0-14 years old in China is 253.38 million, accounting for 17.95% of the total population. This means that when R0 is 6, 100% of people over 14 years of age will be vaccinated, but 85% of the immune barrier will still not be achieved.

So, what if R0 is 9?

Widespread “inoculation hesitation” and “disparity between rich and poor”

In February of this year, COVID-19 data star and independent data scientist Gu Youyang (transliterated Youyang Gu) changed the name of his “COVID-19 pneumonia prediction model” from “Path to Herd Immunity (to’herd immunity’)” to ” Path to Normality”.

He told Nature that healthy people have different views on vaccination. “Vaccination hesitation”, delayed child vaccination, and uneven distribution of vaccines make it difficult to reach the threshold of “herd immunity”.

The Kaiser Family Foundation of the United States released a survey on August 4, showing that among the unvaccinated American respondents, 53% believe that compared with the virus, vaccination poses a greater threat to health.

“Vaccination hesitation” also exists in some parts of China. A survey conducted by the Chinese University of Hong Kong School of Medicine in June this year found that among the unvaccinated population, only a quarter of them intend to complete the vaccination within the next six months. The vast majority of interviewees said that “I have money for vaccination and I don’t want to fight.”

If you look at the world, the difference in vaccination rates can even reach a world of “100 and 0”. Israel is one of the few countries in the world where the vaccination rate has exceeded 60%. In neighboring Egypt and Syria, people who received at least one dose of the vaccine accounted for 1.8% and 0.1% of the total population, respectively.

Matt Ferrari, an epidemiologist at the Center for Infectious Disease Dynamics Research at Pennsylvania State University, told Nature that a perfectly coordinated global vaccination campaign could have eliminated the new coronavirus, which was technically feasible. “But in reality, there are big differences in vaccine promotion efficiency between countries, and even within a country.”

For example, the inoculation gaps in the states of the United States are “high in the north and low in the south”. The one-dose vaccination rate in the northern state of Vermont has reached 75.7% of the state’s total population, but the southern state of Mississippi is only 39.8%.

“We have to consider the geographic structure of ‘herd immunity’.” said Xuevita Bansar, a mathematical biologist at Georgetown University in Washington, DC. If there is a movement of people, there may still be a new outbreak in Israel.”

Has UK’s “gamble” succeeded?

In the early morning of July 29, Zhang Wenhong, director of the National Medical Center for Infectious Diseases and director of the Department of Infectious Diseases of Huashan Hospital Affiliated to Fudan University, wrote an article: In the future, through vaccination, the continuation and recurrence of the epidemic will still not be fully controlled, but if the fatality rate is fully liberalized If it is reduced to the level of influenza, then the serious consequences of the virus epidemic can be eliminated, or the harm of the “COVID-19” can be reduced to the level of seasonal influenza through the establishment of population immunity in a short period of time through vaccination.

He also said: The Nanjing epidemic has made us see the ubiquity of the virus again. Whether we like it or not, there will always be risks in the future. How the world coexists with the virus, each country is making its own answer.

Britain or the first country to hand in the answer sheet. On July 19, the British and England region launched a complete unblocking, and almost all epidemic prevention measures were cancelled: except for a few places such as the subway, other public places are no longer required to wear masks; entering and leaving indoor places do not see negative nucleic acid results; bars, restaurants, etc. Indoor places are no longer restricted to people…

On July 17, the UK added more than 53,000 confirmed cases in a single day, exceeding the peak of the country’s second wave of epidemics in 2020. Based on this, the BBC issued a document stating that “it is a big gamble to unblock it at the time of the surge in cases”. The article also quoted British Prime Minister Johnson’s statement: “There will be more COVID-19 patients hospitalized and died, but considering all factors such as vaccines, seasons, etc., now is the time. If you don’t unblock it at this time, when will you wait?”

Some analysts pointed out that one of the main reasons why the UK “dare to gamble” is its high vaccination rate. The Department of Public Health England (PHE) estimates that 95.5% of the local adult population has been diagnosed with infection or vaccinated and has the COVID-19 antibody.

Two weeks since the unblocking, the “potentially serious consequences” that the chairman of the British Medical Association (BMA), Chad NagPaul, feared, did not appear. On the contrary, the number of cases in many places in the UK has shown a significant decline.

According to data released by the Public Health Department of the United Kingdom, as of August 1, local time, the number of new infections in the United Kingdom was an average of 7 days, a 30% decrease from the previous statistical cycle. Although the number of new deaths in a single day was 24,470, the number of new deaths was 65, a further drop from the “unblocking day”.

As a result, the pace of opening up in the UK has been even greater. From 4 a.m. on August 2nd, people from the United States and European Union countries who have been fully vaccinated with the COVID-19 vaccine will need to undergo nucleic acid testing before departure and the day after entering the UK, but they do not need to be isolated. After August 16th, even if those who have received two full doses of the vaccine are notified as “close contact with the COVID-19 infection,” they no longer need to self-isolate and no longer require mandatory testing.

Many governments and academics, including Israel and Malaysia, believe that the UK’s unblocking strategy is risky, but it shows that in a society that is widely vaccinated, a better balance can be found between keeping the economy open and protecting public health. .

The head of the Israeli government’s COVID-19 epidemic expert advisory group said in late July that “will learn from (the United Kingdom) lessons and take corresponding actions.”

Malaysian Prime Minister Muhyiddin said that he would learn from Britain and other countries to formulate a national recovery plan. “At the peak of the epidemic, the government was gradually liberated. Malaysia’s situation is like the second United Kingdom. The success of the United Kingdom may also be replicated in Malaysia. The prerequisite is the vaccination rate. The British government pays more attention to mortality in the new wave of epidemics, and even It is the rate of hospitalization and severe illness, not the number of new diagnoses. This is to focus on reducing the burden on the capacity of the medical system.”

“As long as the medical system can provide sufficient treatment capacity, it can be opened up.” German Chinese virologist Lu Mengji, a professor at the Institute of Virology at the University of Essen School of Medicine, told China News Weekly that the time for the UK to unblock it is ripe. The COVID-19 epidemic will continue. For people who are not willing or unable to vaccinate, the threat of the COVID-19 virus is permanent, and waiting cannot change this reality. Another point is that there are fewer other respiratory infections in summer, and most people’s immunity is in the best state. Passing the peak of the spread of the COVID-19 epidemic as soon as possible can alleviate the pressure on the health system in autumn and winter.

Some scholars also questioned the existing data in the UK. Dr. Mike Tildesley, a member of the British Government’s Scientific Advisory Group SAGE, and Tim Spector, the main person in charge of the British “COVID Symptom Study” project, agree that the number of new diagnoses in the UK every day is continuous A decline does not mean that the crisis is over. Temporary factors such as reduced testing, school holidays, hot weather, and the end of the European Cup cluster effect may have contributed to the recent decline in cases.

“What we really need to do is to closely monitor the number of hospitalizations. This number is still rising. If the number of hospitalizations also starts to decline, that is more powerful evidence that the third wave of the epidemic is beginning to recede.” Mike Tildesley Say.

A spokesperson for the British Prime Minister’s Office also warned that the actual impact since the complete unblocking has not yet been fully reflected. Prime Minister Johnson stated that it is “too early” to conclude that the epidemic is about to end now.

“China News Weekly” pointed out that with the spread of more transmissible mutant strains and the vaccination rate has not reached the threshold of herd immunity for a long time, the epidemic will be difficult to end. A problem facing policymakers in countries that previously used the zero-clearing strategy is : If you don’t coexist with the virus, what economic and social cost will you have to pay to maintain the current zero infection situation? Many sociologists and bioethicists have proposed that it should be discussed openly how much disease and death caused by the COVID-19 virus can be sustained by society.

In the face of the prolonged COVID-19 epidemic and the “new trend” of COVID-19 health threats, China’s response to the COVID-19 epidemic also needs to be upgraded and adjusted according to local conditions, and “new ideas” need to be considered.

“Herd Immunity of COVID-19” won’t be achieved in a lifetime?!

(source:internet, reference only)

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