Rapid spread of Omicron BA.2: Studies show

BA.2 is especially noticeable in Southeast Asia, Africa and European countries. Recent analysis has replaced BA.1 as the major Omicron subline in Denmark, Singapore, India, South Africa and Austria. The rapid rise in BA.2 gain The prevalence in Denmark went from 20% in the last week of December 2021 to 66% by the third week of January 2022.

The proportion of BA.2 cases in the United States remains Low So far it’s 3.8%, but health experts expect it to rise.

Preprint studies that have not yet been peer-reviewed characterize the differences between the BA.1 and BA.2 subvariants and may explain why the latter outperforms its sibling variants. ..

BA.2 shares many of the mutations in BA.1, but the two subvariants 28 mutationsSome of them are responsible for the rapid surge in BA.2 cases.

Especially, mutation It is also present in peplomers that are unique to these subvariants and mediate the invasion of peplomers. SARS-CoV-2 to cells and the target of the COVID-19 vaccine. Specifically, BA.2 has eight new mutations in the spike protein, but lacks the 13 mutations that the BA.1 spike protein has.

The rapid increase in prevalence of BA.2 in multiple countries suggests that this variant is more contagious than BA.1.In one study, BA.2 was Up to 33% Higher infectivity than BA.1 and its spread Global health In the near future.

Also, nationwide study Comparing the spread of BA.1 and BA.2 variants in Danish households in late December 2021 and January 2022 suggested that the latter was more contagious. The study found that the secondary incidence, which measures the probability that the virus will infect household members, is 39% for BA.2 and 29% for BA.1.

The study also reported it Completely vaccinated Individuals who received booster vaccination were less likely to inherit or become infected due to any of the submutants compared to individuals who were not vaccinated.

In addition, unvaccinated individuals were more likely to spread the BA.2 subvariant to their families than to BA.1.

Domestic infection data from a Danish study show that both vaccinated and unvaccinated individuals were more susceptible to SARS-CoV-2 infection by BA.2 compared to BA.1. It also showed high sensitivity.

The relative increase in susceptibility to the BA.2 mutant was greater in vaccinated individuals than in unvaccinated individuals. In other words, he was more proficient in avoiding the immune protection provided by the vaccine to cause infection.

Talk to Today’s medical newsCo-author of this study, Dr. Frederik Plesner LyngseResearchers at the University of Copenhagen said:[BA.2] Although it has antigenic properties that reduce the protective effect of vaccination against infection, [does] Do not increase infectivity from people vaccinated against breakthrough infections. “

“All individuals are more susceptible to BA.2 than BA.1, vaccination and previous infection status are unconditional. [or both]..Unvaccinated people are more infectious if not vaccinated [acquire an infection] Individuals vaccinated with breakthrough infections (vaccinated and / or previous infections) use BA.2 compared to BA.1. [they contract an infection] Use BA.2 compared to BA.1. “
-Dr. Frederik Plesner Lyngse

The level of antibody that can bind to and neutralize SARS-CoV-2 Predict Degree of protection from infection.two the study Independently shown what individuals immunized with the mRNA vaccine showed Significantly lower Levels of neutralizing antibodies against BA.1 and BA.2 subvariants than the original wild-type SARS-CoV-2.

Upon receiving the third shot as a booster, the neutralizing activity against these Omicron strains was also increased, but the neutralizing antibody level in response to BA.2 was slightly lower than that of BA.1.

Dr. Lyngse said: [acquiring infection]) And infectivity (probability) [causing infections in] Others) —and that booster reduces it even further. “

Considering the slight difference in neutralizing activity against BA.2 and BA.1. Dr. Dan BaruchA virologist at Harvard Medical School and one author of the above study, said:

“The ability of BA.2 to surpass BA.1 is probably due to the increased infectivity of the virus, rather than the additional antigenic escape beyond BA.1.”

Does the treatment work for BA.2.

Researchers have developed a COVID-19 vaccine currently available to elicit an immune response against the wild-type SARS-CoV-2 peaplomer. The reduced neutralizing antibody response to BA.1 and BA.2 in fully vaccinated individuals may reflect a high number of mutations in the omicron spike protein.

These mutations in the Omicron spike protein also explain why most of the monoclonal antibodies that were effective against the previous SARS-CoV-2 mutant reduced their neutralizing activity against BA.1.

Sotrovimab was one of the few monoclonal antibodies that retained neutralizing activity against this mutant.

recently the study Shows Significant decrease In the neutralizing activity of sotrovimab against BA.2 mutants.AstraZeneca antibody combination Evusheld and EliLily antibody Bebuteo Bimab Two approved antibodies that retain activity against both BA.1 and BA.2 variants.

In light of the ability of these Omicron subvariants to evade most therapeutic monoclonal antibodies, scientists have found that further mutations in the SARS-CoV-2 spike protein invalidate all currently available monoclonal antibody therapies. I’m afraid that I might.

Recent laboratory research suggest BA.2 infection can cause more serious illness than BA.1. This study showed that it replicates much faster than BA.1 in cultures of upper and lower airway cells.

Subsequent experiments with hamsters also suggested that BA.2 has a better ability to replicate and spread in the lungs than BA.1. In addition, these experiments caused more lung damage and had a significant negative impact on lung function.

However, so far, data on the severity of human illness suggest that the BA.2 variant does not cause more serious illness than BA.1.

A study Researchers conducted in South Africa assessed the risk of hospitalization for BA.1 and BA.2 infections from December 5, 2021 to January 29, 2022. %. Analyzing the results of 95,470 COVID-19 cases, the study found that similar proportions of individuals infected with BA.1 and BA.2 required hospitalization.

A statement Citing this study and other unpublished real-world evidence from the United Kingdom by the World Health Organization (WHO), DenmarkNote that the BA.2 variant may not differ from BA.1 in its ability to cause serious illness in humans.

The discrepancy between laboratory studies and actual clinical data may be due to the inability of animal models to reproduce all aspects of human COVID-19.

Dr. Larry CoreyA virologist at the Fred Hutchinson Cancer Research Center in Seattle said: “Currently, there is no evidence to suggest differences in the clinical spectrum and course of BA.1 and BA from South African or US locations. 2.”

“Since the BA.2 epidemic began 6-8 weeks later, severity data are delayed. However, to date, there is no evidence of a significant difference and mutual protection between the two variants is very high in the short term. It seems, “he said. MNT..