The Paper reporter He Liping
Israel, as the country with the highest number of COVID-19 vaccinations per capita in the world, less than 2 months after taking off its masks on April 24 this year, due to pressure from BA.5, it is considering reinstating indoor masks. make.
With the Omicron mutant strain BA.5 accounting for 70% in Israel, the number of new daily cases in Israel has once again exceeded 10,000. In late May, Israel's daily new cases dropped to less than 2,000.
On June 19, local time, Israel reported that 10,202 people tested positive for the new coronavirus nucleic acid, with the positive detection rate reaching 27.9%.
Israel New Crown Number of hospital admissions
BA.5 not only has a stronger transmission speed and immune evasion ability, but also can be repeatedly infected. It has a stronger replication ability in human alveolar epithelial cells, which means it is also more pathogenic. Currently, 170 of Israel’s COVID-19 patients are seriously ill, an increase of 95.4% from a week ago.
Nachman Ash, director-general of the Israeli Ministry of Health, said on June 19 that a new wave of infections may have arrived. Nachman Ash noted that in the early stages of the new wave of the epidemic, the Ministry of Health does not intend to impose broad restrictions on large gatherings as it did previously. However, the Ministry of Health is considering reintroducing mask mandates in enclosed public spaces.
As BA.5 takes hold in Israel, Israeli experts say the possibility of including a fifth shot for the elderly and immunocompromised people should be considered.
In fact, the BA.4 and BA.5 mutant strains of Omicron have also suddenly emerged in the United States, setting off a new wave of infections.
The latest data from the US Centers for Disease Control and Prevention shows that as of June 11, the combined share of BA.4 and BA.5 in the United States reached 21.6%. On May 7, the combined share of BA.4 and BA.5 in the United States was only 1%. This means that within 35 days, the combined share of BA.4 and BA.5 surged 21 times. Among them, BA.4 accounts for 8.3% and BA.5 accounts for 13.3%.
The European Center for Disease Control and Prevention recently stated that BA.4 and BA.5 spread faster than other Omicron variants and may lead to more hospitalizations and deaths.
BA.4 and BA.5 have a key mutation in the spike protein: L452R. The L452 site mutation is not found in the Omicron BA.1 and BA.2 mutant strains, but is the spike protein mutation site possessed by Delta (Delta). The spike protein plays a key role in the entry of the new coronavirus into human cells: it can bind to the ACE2 receptor of human cells, invade across the cell membrane, and is the "key" to open the door of the cell. It is also the "key" to the human immune system, , mRNA vaccines and The main target of the antibody drug .
Currently, BA.4 and BA.5 have become the dominant mutant strains in Portugal. Although Portugal’s vaccination rate exceeds 85%, it has just experienced the outbreak of Omicron BA.1 and BA.2 from the end of 2021 to the beginning of 2022. Despite the large number of infections, Portugal still saw a new wave of infections, and the positive detection rate was once as high as 50.63%. The number of new deaths has also returned to the level at the peak of Omicron infections in January and February 2022.
Extended reading: BA.4/5 can replicate efficiently in human alveolar epithelial cells
Research on the pathogenicity of BA.4/5 was previously obtained from University of Tokyo , Kyoto University , Hokkaido University , Kyushu University , Kobe University , Israel's Weizmann Institute of Science and other 27 scientific research institutions jointly published a blockbuster study on the medical preprint website bioRxiv, showing that the replication efficiency in human alveolar epithelial cells is higher than that of BA.2, especially It is that BA.4 and BA.5 have stronger cell fusion ability in alveolar epithelial cells than BA.2.
In order to test the replication ability of many mutant strains of Omicron in human alveolar epithelial cells, the research team prepared chimeric recombinant SARS-CoV-2 virus with L452R mutation through reverse genetics. Experiments showed that The plaques formed by BA.4 and BA.5 infection of human alveolar epithelial cells were larger than those formed by BA.2 infection. The researchers also found through experiments that BA.4 and BA.5 are much more efficient than BA.2 in replicating in human iPSC-derived alveolar epithelial cells.
Extended reading: Breakthrough infections and re-infections of Omicron
The Omicron variant of the new coronavirus has swept the world, infecting hundreds of millions of people.Since the symptoms caused by Omicron are milder than Delta, and natural infection can bring about a certain degree of immunity, some people believe that the Omicron mutant strain is a natural booster shot. However, the latest research reveals that the effect may be exactly the opposite: infection with the Omicron variant after vaccination may not lead to immune enhancement, and may also weaken immunity to new mutant strains in the future.
The above conclusion comes from a recent blockbuster study published in the authoritative international academic journal "Science", "Immune boosting by B.1.1.529 (Omicron) depends on previous SARS-CoV-2 exposure).
The study, led by researchers at Imperial College London, UK, looked at how complex patterns of population immunity following vaccination and previous infection affect people's future protection against SARS-CoV-2.
The official website of Imperial College London stated that this study found that the immunity brought by infection with Omicron was very poor in the natural immune enhancement provided by Omicron reinfection itself, and even after receiving 3 doses of the vaccine, it was The same is true for people who are sexually infected with Omicron.
The core issue is "Immune imprinting". In layman's terms, the body's immune pattern against the new coronavirus will be "imprinted" on the immune system through the history of infection. Each person's immune signature depends on the number of vaccine doses they receive and the variants to which their infection is exposed. This leads to varying immunity in different individuals within a population.
An individual's history of prior SARS-CoV-2 infection affects the ability to become immune to subsequent SARS-CoV-2 infection through a process called "immune imprinting," which also applies to the numerous sub-variants of Omicron, Includes BA.4 and BA.5. The "immune signature" of the Alpha variant (Alpha, B.1.1.7) early in
infection resulted in a reduced persistence of binding antibodies against Omicron. Danny Altmann, author of the
paper and professor in the Department of Immunology and Inflammation at Imperial College London, said, "We found that the Omicron variant is far from being a natural, benign booster of vaccine immunity as everyone might have thought before. On the contrary, it is a special Hidden immune evaders. ”
In those who have received three doses of the vaccine and have no previous infection with the new coronavirus, Omicron infection can provide protection against previous variants (Alpha, Beta, Gamma, Delta and original ancestor strains). Immunity boosted, but less immune to Omicron itself. Those who were infected during the first wave of the pandemic and who were later reinfected with Omicron showed no boost.
The findings may help understand why breakthrough infections and superinfections with and are common among Omicron variants. However, the study stresses that vaccination continues to provide protection against severe disease and death.
has previously analyzed that even if the antibody recognition ability against Omicron is poor, the body's T cell immunity may be ready to fill the gap to achieve effective protection. However, the study showed that in those infected with Omicron, their T cells recognized the Omicron spike antigen less well. Professor Rosemary Boyton from the Department of Infectious Diseases at Imperial College, corresponding author of the
paper, said, "Infection with Omicron does not effectively improve immunity to future Omicron re-infections."
Altmann said, "Omicron Not only can Cron break through vaccine defenses, but it also appears to leave very few of the signatures we expect on the immune system. OmiCron is more subtle than previous mutant strains, and the immune system seems unable to remember it."
Editor-in-Chief: Li Yuequn.
proofreading: Liu Wei
