Xinhua News Agency, Beijing, September 29, a new media special report on the US "Wall Street Journal" website on September 20 published a report entitled "How to achieve herd immunity to curb the new crown pneumonia epidemic".
The content is summarized as follows:
Herd immunity will not happen soon
The concept of herd immunity is at the core of global vaccination efforts, as well as discussions on the next steps to prevent the new coronary pneumonia pandemic and restore the economy.
Public health authorities estimate that to achieve herd immunity against the new coronavirus, approximately 60% to 70% of people in a specific population need to have an immune response to the virus.
Some epidemiologists and mathematicians now say that the group effect may appear before then, possibly close to 50%, which indicates that potential protection can be achieved faster.
However, infectious disease experts firmly warn people not to try to obtain herd immunity against the new coronavirus without being vaccinated, because this will cause an alarming loss of life, and herd immunity is likely not to happen soon.
Even with vaccines, there will still be obstacles in achieving herd immunity.
Saad Omar, director of the Yale University Institute of Global Health, said: "This is an ongoing process. Before this tipping point, you may start to see (an effect), but another question is possible. There will be small-scale outbreaks."
He said: "This is not to say that once herd immunity is achieved, we won't have new coronary pneumonia."
The human immune threshold is mathematically determined by the infectivity of the virus, that is, how many people will be infected by each infected person-also known as the basic reproduction number.
Scientists used this number and an equation proposed by two Scottish epidemiologists nearly a hundred years ago to calculate the herd immunity threshold.
For example, measles is extremely contagious.
Its basic regeneration number is between 12 and 18, and its herd immunity threshold is 90% to 95%.
For the new coronavirus, its basic reproduction number is estimated to be between 2.5 and 3, which means that the herd immunity threshold is 60% to 70%.
In fact, people live together and only interact with certain people.
Age, work, social networks, and even the individual's biological response to infection will affect a person's position in the disease transmission network.
Epidemiologists say that if people who are more likely to spread the virus acquire immunity early (whether through infection or vaccine), then it is possible that a decline in transmission capacity will begin sooner.
It is strongly recommended not to relax restrictions
A group of researchers estimated that the threshold for the new coronavirus may be as low as 10% to 20%, although many epidemiologists say this is unlikely.
Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, said his research team estimates that the threshold for herd immunity is between 50% and 80%.
Paul McKeeger, professor of genetic epidemiology and statistical genetics at the University of Edinburgh in Scotland, said that if the lower estimate of herd immunity is correct, then governments should consider introducing policies to relax restrictions on others while protecting High-risk groups such as the elderly are protected from the virus.
However, most infectious disease experts strongly advise against this because it is unclear how the government will protect the more vulnerable populations from the virus.
Nadia Abu Elezam, an infectious disease-epidemiologist at Boston College in the United States, said: "If we are talking about letting this disease develop naturally (and) infect a large number of people, then fundamentally, what we are talking about It is that the public health system is not playing its due role. We will have many deaths and many people will become ill."
Epidemiologists say that even if the grouped population does have certain protective immunity, the virus can easily jump into groups that have not been exposed to the virus, especially if restrictions are relaxed and people may start to socialize and travel more.
Natalie Dean, a biostatistician at the University of Florida who specializes in infectious diseases, said that where the growth rate of cases has slowed, changes in behaviors such as wearing masks and maintaining social distancing are more likely to explain the decline in cases.
For example, Sweden has not implemented a strong blockade, but still bans gatherings of more than 50 people. There are other restrictions and voluntary guidelines.
A preliminary survey conducted by the Swedish Public Health Agency in May showed that the proportion of people between the ages of 20 and 64 and those between the ages of 65 and 95 who had antibodies was only 6.7% and 2.7%, respectively.
Sweden’s per capita mortality rate is also the highest in Northern Europe.
The immune protection effect is unclear
Another problem is that infectious disease experts are not sure how long the immunity to this virus can last, nor how often reinfections are.
Exposure to other coronaviruses in the past may provide some protection, although the effectiveness of this protection is unclear.
For diseases such as measles, mumps and polio, herd immunity is indeed achieved through vaccination campaigns.
Many people say that the US Food and Drug Administration (FDA) may approve a new crown vaccine before the end of the year, but this is likely to be delayed until 2021.
Even if it is possible to obtain a vaccine, there is growing concern that some Americans do not want to be vaccinated.
How many people need to be vaccinated to help achieve herd immunity also depends on the effectiveness of the potential vaccine.
The FDA has indicated that it will approve a vaccine with an efficacy of 50% or higher.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said: "With quality vaccines and good public health measures, we may be able to get rid of this virus outbreak. This will end and we will be able to return to normal."