One wave is not flat, one wave rises again. Novel coronavirus has mutated again in once again. Although foreign virus changes will not immediately affect China. But seeing these news, I always have a feeling of chest tightness and weakness. Human beings try their best, how can the enemy fight more and more fiercely? The virus is so smart, can we withstand it?
Source: microblog @ China News
It's not a mutation
But only strong mutations can be identified
The COVID-19 has lasted for more than two years. We have also remembered many Greek letters and English abbreviations. From the early alpha and delta to the present ba 2.12.1 it seems that every time we notice these virus changes, there are words of "stronger" and "super strong".
This is not the initiative of novel coronavirus to seek innovation and change. The virus mutates randomly and disorderly. Only the strong can stand out in the cruel competition and seize more opportunities to infect the human body. More virus variants can not infect people, so they can only eliminate all the viruses. Even if it is detected by humans accidentally, it will soon disappear in the long river.
A few lucky people who have changed by chance can become the mainstream novel coronavirus in the world and become the protagonist of media reports.
Novel coronavirus has experienced alpha, Delta and Omicron ba 1. Omicron ba 2. The mainstream period of. Today, Ba is still used in most countries 2 is dominant, but from the trend, there are indeed three new "stronger mutants" emerging slowly.
Source: covariants
21k in the picture is the original strain Ba of Omicron 1, 21 L is ba 2。 22A is ba 4, 22b is ba 5, 22c is the protagonist of today's news ba 2.12.1。 They are all new variations based on Omicron
BA. 2.12.1 mainly concentrated in the United States, BA 4 and ba 5 are mainly distributed in South Africa. Although we can see the growth trend, will they replace BA in the future 2 has become the world's leading mutant, which can not be determined at present.
The "30% higher infectivity" transmitted online is not accurate
BA. 4，BA. 5，BA. 2.12.1 the prevalence of these three new variants in some areas shows that they are indeed powerful, otherwise they will not replace the original variants.
In Ba 2.12.1 (red bar) for example, in the past few weeks, it has been eating away at BA in the United States 2's sphere of influence will soon reach half of the infection.
Source: CDC
We can use the concept of relative growth rate (RDR) to express ba 2.12.1 growth. During this period, different statistics believe that ba 2.12.1 compared with BA The RDR of 2 ranged from 25% to 38%. This may be the source of 30% of the hot search.
Strictly speaking, this is not ba The infectivity of 2.12.1 was 30% higher. Only in the current American environment, BA 2.12.1 the final propagation result is better than the original ba It's about 30% faster. Because of Ba 2.12.1 it spreads faster, so it has gradually become the mainstream of the virus.
Faster actual transmission does not mean stronger infectivity, because in addition to the infectivity itself, different human immunization and control policies will also affect the actual transmission capacity.
The infectivity of virus is usually expressed by R0 value (basic infection number) It refers to how many people can be infected by a person infected with the virus without protection. This is a naked infectious competition, in a completely consistent environment.
In the early stage of the COVID-19, human beings had no immune protection ability, only a little influence of the physical isolation policy. Therefore, the variants that could become the mainstream were basically highly infectious. R0 values are 1.4 ~ 3.8 of the original strain, 4 ~ 5 of alpha, 5.1 of delta, 7 of Omicron
After Omicron, infectivity cannot be directly equal to transmission capacity. Because the world has changed.
Strong immune escape is the key to rapid transmission
Before and after the Omicron period, the vaccination of new coronavirus vaccine in major countries in the world has reached a high level, which is equivalent to the establishment of a layer of active immunization.
More importantly, Omicron basically broke down the protection of various countries, from some people infected with the new crown to almost universal infection. Although the statistics show that there are hundreds of millions of new infections in the world, more are not detected and not reported after antigen testing, resulting in a large number of missing statistics. It is estimated that two-thirds of people in the United States have experienced infection.
Estimated true coronavirus infection rate of all ages in the United States photo source: Nature
In the United States and many other countries in the world, there have been passive universal immunization against novel coronavirus, or novel coronavirus Omicron strain.
On this basis, if we want to defeat the same species and win the competition, the strongest ability of the mutant is no longer endogenous infectivity, but immune escape ability. Only by better defeating the human immunity that has been actively protected by the vaccine and experienced in virus infection can the new mutant "win".
BA. 2.12.1、BA. 4、BA. 5 because of the stronger immune escape ability, it began to replace ba 2 and the original Omicron are expected to become the mainstream of the world Their true infectivity, R0, is unclear.
Chinese scholars have played an important role in explaining the immune escape ability of the three.
The team of academician Xie Xiaoliang of Peking University has uploaded a detailed study on the evasion of immunity of new variants on the preprint platform, which is expected to be published in cell. The study confirmed that Omicron virus can mutate and specifically escape the immunity brought by the original strain, and can also escape the immune protection from three shot vaccination. The key to escape immunity is l452 mutation. BA. 2.12.1 l452q, BA 4/BA. 5 is l452r.
For a long time in the future, the variation draining the mainstream of the new crown will still be the strong immune evasion.
Is the new mutation good for the world? Is it bad
Just after a round of national baptism of Omicron, there is a new mutation to escape immunity. It seems that the world will not be good.
Not exactly.
The current variation seems to occur frequently. In fact, it is also held in the palm of human hands to a certain extent. It belongs to "predicted variation".
Dr. Trevor Bedford, who is dedicated to the study of virus transmission and evolution, has roughly given this change pattern in a series of predictions of novel coronavirus, which has been gradually verified in the real world.
Image source: speculation published by Trevor Bedford on April 7
Although novel coronavirus has various variations, its structure is limited after all. With constant random attempts, the emergence of Omicron has brought mutation to a new level, and it is difficult to play big tricks again.
In other words, novel coronavirus has found the most suitable survival mode for human society. In the short term (Trevor Bedford predicts that the epidemic period of Omicron will be 1.5 to 10.5 years) there will be no uncontrollable mutations we are worried about, so there will be no obvious fluctuations in pathogenicity, but just some fine-tuning to avoid immunity. After Omicron, the next big variation that will be named by Greek letters will not come easily.
Although these fine adjustments have also made mankind a little passive, they will not seriously affect society and become a variety of human and ba Stable attack and defense of XXXXXX.
It can also be seen from the figures of the United States and South Africa in the last month that the number of new infections has increased under the influence of new mutants, and many of them are repeated infections. But the number of hospitalizations and deaths did not rise significantly.
Us new crown hospitalization curve since March 2020 source: Twitter @ Eric Topol
Of course, even with fine-tuning, these immune escapes have brought major problems to our vaccine research and development.
Judging from the current rapid variation, the Omicron special vaccine launched for Omicron a few months ago may be difficult to play a role. The rapid change makes any special vaccine a thing of the past.
To better increase the active immunization of the vaccine, the current multi vaccine intensive vaccination may achieve better results (the vaccine developed for the original strain is more resistant to all kinds of Omicron mutations). In the future, there should be more optimized multi-stage vaccines, or new vaccines that can span all variants.
What about China
Many countries in the world have experienced the transit of Omicron and established passive immunization after painful losses. In China, only a small number of people in some areas have this kind of passive immunization, and what they can rely on in the future is vaccine protection.
Now Shanghai and other places are fighting ba 2. There may be ba in the future 2.12.1 in, and other possible new variations. If our strict prevention can not stop the virus, with the current limited vaccine protection, it is likely to usher in a case tsunami.
According to a modeling article of Omicron popular in China published on Nature Medicine by the school of public health of Fudan University, the new crown will lead to the collapse of the medical system and a significant increase in the number of hospitalizations, ICU occupancy and deaths. Among them, the peak demand for ICUs will be 15.6 times the current number of ICUs, with a total death toll of about 1.55 million, of which 77% are people who have not been vaccinated**
If the vaccine coverage rate of the elderly population is increased (vaccinating the currently eligible people with the existing supply of vaccines, including whole course vaccination and booster vaccination), the number of hospitalizations, ICU occupancy and deaths can be reduced by 33.8%, 54.1% and 60.8%.
It is difficult for us to quickly improve the treatment capacity of ICU in the short term. In order to protect 1.55 million lives, the key is to continue to promote vaccination.
More vaccine supplies, more advanced vaccination methods and richer types of vaccines have effectively improved the vaccination rate of the whole people, so as to have more confidence to meet possible changes in the future and win another victory in the fight against the epidemic.