The Paper's reporter Liu Dong
On July 6, the World Health Organization (WHO) released the latest global COVID-19 weekly report showing that the number of new coronavirus cases worldwide increased for the fourth consecutive week, reaching the highest level since March this year, and the main reason for the increase in the number of cases is that the more infectious and immune-evasive Omilon BA.4 and BA.5 variants have triggered a new wave of infections around the world.
As of 3 July, who obtained statistics on global genetic sequencing samples of COVID-19 show that the proportion of BA.4 and BA.5 variants continues to increase, with BA.5 growing faster and has been detected in 83 countries, accounting for 52% of all samples (37% last week), while BA.4 accounts for 12% (last week: 11%). At present, BA.5 has replaced BA.2 as the world's leading strain.
The Centers for Disease Control and Prevention estimates that as of July 2, BA.4 and BA.5 accounted for 70 percent of existing COVID-19 cases in the United States. Among them, BA.5 accounted for 53.6%.
On July 5, the Xi'an Municipal Center for Disease Control and Prevention in China reported that the genetic traceability of the virus in Xi'an showed that the variant strain of the epidemic was the BA.5.2 branch of Theomilon. This is also the first time that China has reported that the subtype of the Aomi Kerong BA.5 subtype is endemic in the homeland, and there has been community transmission.
WHO says the proportion of BA.4 and BA.5 variants is still rising, which is related to their strong ability to contagious and immune escape, especially their ability to evade vaccination and immunity from previous infections.
Eric Thompson, director of scripps research and translational research in the United States, said that he would not be able to do so. Eric Topol, a medical expert who has long been concerned about COVID-19, admits: "BA.5 is the worst version of the mutant we have seen so far. It takes the already widespread immune escape to new levels and enhances infectivity far beyond the Aumechjong mutant we've seen before. ”
The global pandemic is on the rise again
Why is BA.5 the worst?
This may be another major mutation in the evolutionary history of the new crown virus: the ba.5 mutation has gained a stronger immune escape ability to make it the new global "strain overlord", and the last time such a major mutation was the Omicron BA.1 that appeared last November, which replaced the Delta mutation in the following months, setting off a wave of outbreaks around the world.
In an article published on the institute's website, Topol called BA.5 the "worst COVID-19 strain to date" and explained that it was largely based on BA.5's immune escape ability and no less intrinsic ability to spread than its "predecessors."
First of all, from the perspective of genetic distance, Topol pointed out that in the evolutionary route of the new crown virus, BA.4/5 evolved on the basis of BA.2; and BA.2 was not directly derived from BA.1.
Omikron BA.5 genetic evolutionary distance
Therefore, BA.4/5 also has a strong immune escape against the serum of BA.1 infected people. This means that people who have recovered from previous infections with BA.1 are also vulnerable to re-infection. This has been confirmed in South Africa, where BA.4/5 and BA.1 were first discovered.
Then there is the antigen atlas. The new coronavirus S protein is a key viral structure recognized and bound by the human immune system, and the antigen distance of the new coronavirus mutant strain can be depicted according to its differences. Topol pointed out that BA.1 has already undergone a very strong immune escape, and BA.4/5 has a strong immune escape on the basis of BA.2, making the antigen very far away from the original strain.
At present, most of the vaccines are based on the original strain and ba.1S protein, so the antibody effect against BA.5 is very low, and the protective effect can be imagined.
For these reasons, BA.4/5 has a strong immune evasion ability for the existing "immunity wall" in the population, and coupled with its ability to infect its predecessors, it will almost certainly trigger a new wave of epidemics around the world.
The antigen map shows that the Aumicon BA.5 has drifted significantly
Mutation is accelerating
Topol notes that existing studies have shown that the difference between BA.5 and BA.1 and BA.2 is much greater than the difference between delta, beta and gamma variants and the original strain.
There was a full year and a half between the original strain and the appearance of Delta, and BA.5 appeared less than half a year after the emergence of the Omikeron BA.1 variant. This suggests that virus mutations are becoming faster and more frequent.
In South Africa, where BA.5 first appeared, BA.5 quickly became the dominant strain, followed by Portugal and other European countries. Since the rise in BA.5 and the decline in BA.2 occur almost simultaneously in many countries, and the proportion of BA.2 varies between countries, the rise in BA.5 is often masked.
But it's not just the aforementioned countries that have seen the growth of BA.4 and BA.5 — that's happening all over the world, and it's happening very quickly. In addition to the United States, data released by the United Kingdom on July 2 showed that despite previously achieving higher levels of "herd immunity", the number of confirmed COVID-19 cases reported in the country surged by more than 30% last week due to the spread of BA.4 and BA.5.
Another important question is whether BA.5 is more toxic and pathogenic. Can it induce more serious disease? In response, WHO said in its latest weekly report that so far, there is no evidence that BA.5 causes heavier or lighter diseases.
On June 28, South African scientists published the first article on the severity of the condition of a BA.4/5 infected person on the pre-print open platform medRxiv. The researchers compared cases during the Omicron BA.4/5 epidemic from 1 to 21 May 2022 with laboratory-confirmed cases during previous outbreaks. The results showed that there was no difference in the risk of morbidity/critical illness in BA.4/5 cases compared with BA.1 cases, and all were lower than earlier strains.
How much protection do current vaccines have against BA.4 and BA.5? Many governments and scientists have begun to study and address this issue. While WHO stresses that conclusions should be drawn with caution, Topol said it would not be surprising if vaccines were further reduced in protection against hospitalizations and deaths, given the nature of BA.4 and BA.5.
Hospitalization rates are once again rising around the world
What are we going to do?
For the spread of BA.4 and BA.5, Topol's advice is: wear a high-protection mask (N95/KN95); Social distancing; Vaccinations are given to boost the needle.
According to the U.S. Centers for Disease Control and Prevention, a fourth dose of the vaccine for people over the age of 55 can reduce the risk of death by a factor of 4 on the basis of 2 or 3 doses, however, not all people can or are willing to receive a booster dose.
Another key question is: In the face of BA.5, which has a strong immune escape ability, do we have to wait to develop a specific vaccine against BA.5?
The biggest problem is "time". The development of the Omilon BA.1 booster needle took more than 7 months, and when it was developed, it was already the time when the BA.1 vaccine had been seriously escaped by BA.5.
Similarly, the focus is now on BA.5, and no one can guarantee that after a vaccine against BA.5 is developed, what will the mainstream strains look like then?
However, Trevor Bedford, an expert in virus evolution, who supports the development of the BA.5 vaccine, said on social platforms that although there is no doubt that the new coronavirus will continue to evolve, the new strain is most likely to evolve on the basis of BA.4/5, so the development of a BA.4/5 specific vaccine is both necessary and sustainable.
Novavax, a U.S. vaccine development company, expects to offer a COVID-19 vaccine tailored to the Ami kerong BA.4 and BA.5 variants in the fourth quarter of this year.
In addition, Topol also pointed out again: the development of oral and nasal inhalation vaccines is very critical to induce mucosal immunity, so as to block the chain of transmission at the beginning of infection. And that's what we're currently lacking.
Editor-in-charge: Hu Zhenqing Photo Editor: Shen Ke
Proofreader: Yan Zhang