Omikeron will soon infect 60% of Europe's population
In terms of the number of infected people, it is really a huge group
So here's the problem —
Today we will talk about it
Herd immunity, what exactly is it?
When a pathogen that most people have never seen
(Viruses, bacteria, etc.) enter human society
It's like there's a little Mars in the forest
At this time, dry firewood was everywhere
The spark is triggered
These fires, in turn, act as part of the chain of propagation
Lighted nearby dry firewood
Wave after wave
The forest is on fire...
The same is true of the spread of infectious diseases
All are susceptible
All are at risk of infection
And these infected people serve as new sources of infection
Transmit the pathogen to more people around
The situation gradually spirals out of control
We call it the "outbreak."
Herd immunity is
A large part of the population has gone from dry wood to —
stone
If most of it is dry wood
Turned into stone
The fire could not continue to spread
Forest fires will soon be extinguished
Those who are resistant to pathogens are the stones in it
It's like a stone in a forest fire
This group of people --
You will not get sick, you are safe
Block the pathogen's chain of infection
Does not transmit pathogens to those around them
These people form a protective barrier
The spread of infectious diseases is hindered
All the people were protected
Not just the stones in it
Including dry firewood that was once threatened by fire
What is the herd immunity barrier?
When a group is on some kind of infectious disease
The percentage of individuals with resistance reached a certain value
It protects other individuals in this group
Protected from the infectious disease
This concept is called the "herd immunity barrier"[1]
People with immunity in the body are like a wall
Isolate people who are not immune from the pathogen
In the population, the higher the proportion of people who are immune
The thicker the wall, the thicker it is
Analyze it from a scientific point of view
There is nothing inherently wrong with herd immunity theory
It is a great theoretical breakthrough in the history of infectious disease prevention and control
Guided by this theory
Prevention and control of an infectious disease
We just have to guarantee
A certain percentage of the population gains immunity
This can build an immune protective barrier
Infectious diseases do not have widespread outbreaks
It can even be wiped out
Through herd immunity
We have succeeded in controlling many terrible infectious diseases
For example, smallpox, polio, diphtheria, etc
They have almost no impact on us now[2-3]
The problem is
How do I gain immunity to an infectious disease?
There are two ways[1]:
One is vaccination
Thus safely gaining immunity
The second is to let some people be infected
But there are great risks associated with this
The second is the view
When pathogens ravage in society
A group of people became ill after infection
Those who survive gain immunity
Until when there is immunity in the body of the person
Reach a certain percentage in the population
When the immune protective barrier is successfully established
Everyone is safe
You might ask:
What if someone can't stand it?
- I can only apologize
The second is the reason why "herd immunity" is so controversial today
A group of medical scientists published the Great Barrington Declaration.[4]
(Great Barrington Declaration)
Renewed call for herd immunity -
They think
The coronavirus should be allowed to spread among young healthy people
Young people after infection
The risk of severe illness and death is low
And these young people fell ill and recovered
You have immunity
When the number of young people with immunity reaches a certain percentage
Everyone — including the elderly and the infirm —
The risk of contracting the virus is reduced
October 12
WHO Director-General Tedros Adhanom Ghebreyesus said —
First of all, ethically, this way is immoral
The premise of forming a herd immune barrier is -
A certain percentage of people have become immune to pathogens
As for how many people?
Different pathogens differ due to their infectious strength
The proportions required are not the same
This is called the "herd immunity threshold."
Wu Zunyou, chief expert in epidemiology at the Chinese Center for Disease Control and Prevention
A published paper shows
At least 47% to 85% of the population needs to be infected
In order to achieve the protective effect of herd immunity
End of the epidemic[5]
Say
These people have to bear it
The terrible health risks of contracting the new crown virus
According to statistics
After a young person under the age of 60 is infected with the new crown virus
Average mortality rate was 0.6%[6]
According to herd immunity theory
Let the coronavirus be left alone
Spread among healthy people and young people
No restrictions are imposed
There is no restriction on social distancing
It is assumed that all infected people are under 60 years of age
When the proportion of infections reaches 60% of the world's 7.8 billion people –
About 20 million people will die worldwide
However, such a huge number of deaths
All due to the unrestricted spread of the virus
and resulting in unnecessary death
Everyone who dies
They are an indispensable part of every family
This is also what Tedros called moral infeasability
Scientifically, this approach is difficult to work
The theory is to infect young people
Forms an immune protective barrier
But the reality is often complex
One
It is impossible to precisely control the age of infected people
And rely on infection to achieve the desired proportion of the population
It can take a long time
WHO noted in a media release
The rate of COVID-19 infection in most areas is less than 10%
Dense transmission areas reached 20%-25% or higher
Well below the 70% infection rate
(World Health Organization's regular briefing on 12 October, Maria van Kokhov, Technical Director of the Health Emergencies Program)
Serological epidemiological investigations can help
Learn about covid-19 infections in a population
June and July studies showed
Despite being exposed for months
But antibody investigations found
Spanish and Swiss urban populations in serum
The positive rate of antibodies specific to the new coronavirus is low
Less than 10%[7]
Two
Nor is it considered here:
The effects of diseases on the human body
It's not just death
On October 12th
At a regular WHO briefing
Introduction of the technical director of the health emergency project
At present, mild patients have been identified
Recovery from infection may also have long-term effects on the body —
Including the heart, brain, lungs, etc
For humans
The coronavirus is a completely new virus
How much harm does it really hurt the human body?
It's not entirely clear at this point
Three
Immunity acquired after infection
Whether there is lasting protection is still unknown
There are already people in the world who have been infected with the new crown virus and recovered
Secondary infections have been reported[8]
It has also appeared recently
The world's first case of death after a second infection with THE new crown virus
Dutch researchers report
An 89-year-old woman in the Netherlands dies after a second infection with COVID-19[9]
Herd immunity is about protecting people from pathogens
Instead of letting people actively contact the pathogen
Get vaccinated against COVID-19
it is the ideal way to achieve herd immunity
For vaccinators
Vaccines can produce immunity
Without causing illness or enduring complications of infection
Not only protect yourself
It also protects people who cannot be vaccinated
For example, for newborns or people with compromised immune systems
Reading this, I think we all know it
People don't need 100% vaccination
As long as a certain percentage is reached
It can interrupt the chain of transmission and extinguish the epidemic
Exactly how many people need to be vaccinated,
We did the math:
Other words
Globally, about 5.5 billion people need to be vaccinated
There are about 1.05 billion people in the country
Even with vaccines
In the process of achieving herd immunity
For a long time
Vaccines merely mark a slow remission of the outbreak
It doesn't disappear like a magic potion
If the protective time of the vaccine is short
Frequent vaccinations are required
This is exactly what is very likely to happen
For example, influenza viruses are highly variable
Annual vaccinations are required
Until then
It is important to delay the spread of the virus and protect people at high risk
Although the epidemic has been with us for a long time
But in the face of the epidemic, there is no shortcut
There is also no one-size-fits-all approach
But actually
It's also very simple
Wash your hands frequently and wear a mask
Try to go to crowded places as little as possible
The country has survived the most difficult time with this
And the COVID-19 pandemic is still under control
Reviewers:
Luo Tianming | Postdoctoral Fellow, School of Basic Medicine, Peking University Health Science Center
Zhang Can has a | Ph.D., Peking University School of Medicine, Assistant Researcher, Chinese Center for Disease Control and Prevention
bibliography
[1] Herd immunity and COVID-19 (coronavirus): What you need to know. [EB/OL] mayoclinic.org. 2020.
CDC. Overview of the epidemic situation of notifiable infectious diseases in China in 2019. [EB/OL] nhc.gov.cn. 2020.
CDC. Overview of the epidemic situation of statutory infectious diseases in China in 2018. [EB/OL] nhc.gov.cn. 2019.
[4] The Great Barrington Declaration. [EB/OL] gbdeclaration.org. 2020.
Wu Zunyou. Feasibility analysis of herd immunity as a strategy for the prevention and control of novel coronavirus pneumonia. Chinese Journal of Epidemiology, 2020, 41(7): 986-989
Epidemiology Group of Emergency Response Mechanism for Novel Coronavirus Pneumonia, Chinese Center for Disease Control and Prevention. Epidemiological characteristics of novel coronavirus pneumonia[J]. Chinese Journal of Epidemiology, 2020, 41(2): 145-151
[7] Jones D, Helmreich S. A history of herd immunity. [J] Lancet. 2020, 396(10254):810-811.
[8] Iwasaki A. What reinfections mean for COVID-19. [J] Lancet Infect Dis. 2020, online.
[9] CCTV-2 Financial Channel. The Netherlands reports the world's first case of covid-19 deaths from secondary infection. [EB/OL] tv.cctv.com. 2020.