February 26, 2024

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New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems

New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems


New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems, and have spread to more than 20 countries.

With the large-scale epidemic of the new coronavirus, new virus mutants continue to emerge, such as Alpha, Beta, Gamma, Delta, Omicron, etc., some of which have stronger infectivity or stronger immune escape ability.

At present, the world’s most concerned about the Omicron mutant strain. The Omicron mutant virus is causing another wave of bloody storms around the world. The domestic epidemic is heating up, and many cities have been re-blocked.


South Africa has seen a surge in the number of confirmed cases of Covid-19 in the past week and may be entering its fifth wave of Covid-19.

This wave of outbreaks was driven by the Omicron BA.4 and BA.5 strains, a newly discovered subtype that appears to be more contagious than the earlier BA.2 strain.

Although the BA.4 and BA.5 variants are not currently listed as variants of concern by WHO, their spread will be monitored very closely.

On May 1, 2022, researchers from the African Institute of Health in South Africa published a research paper titled “Omicron sub-lineages BA.4/BA.5 escape BA.1 infection elicited neutralizing immunity” on the preprint platform medRxiv .

This study shows that Omicron variant strains BA.4 and BA.5 can evade vaccine immunity and the natural immunity of early infected persons. Based on neutralization escape, BA.4 and BA.5 have the potential to cause a new wave of infections. This means that people who have been vaccinated before or who have had the COVID-19 may be infected with the new Omicron mutant strain .


New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems


For the study, researchers analyzed blood samples from 39 patients infected with the original Omicron, 15 of whom were vaccinated, 8 were vaccinated by Pfizer, 7 were vaccinated by Johnson & Johnson, and 24 were not vaccinated vaccine.

The study found that when tested against the BA.4 and BA.5 sublineages, the production of neutralizing antibodies fell nearly eightfold in blood samples from unvaccinated people previously infected with the original Omicron variant, compared with vaccinated people. of samples showed an approximately three-fold reduction.


New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems


Low absolute neutralization levels of BA.4 and BA.5, especially in the unvaccinated group, are unlikely to protect against symptomatic infection well, the researchers said.

This may suggest that BA.4 and BA.5 have the potential to lead to a new wave of infections based on neutralization escape.

The World Health Organization said on the 28th that the number of COVID-19 cases has risen sharply in Africa. Especially in South Africa, Omicrona variants BA.4 and BA.5 are spreading rapidly.

Data from South Africa showed that these two subvariants accounted for only a small percentage of Omicron samples detected in February, 0.34% and 0.08%, respectively.

But in March, these two subvariants accounted for 14% of the total sample, and in April the proportion had reached 44%.

On April 28, South Africa had recorded more than 6,300 new cases, with a positivity rate of 21%. This is the highest value in nearly three months, and 90% of South Africa’s population is immune-protected.


South African expert Tulio de Oliveira, the first scientist to discover the Omicron variant, noted that BA.4 and BA.5 share the same spike protein as the now-dominant BA.2, but BA.4 and BA.5 have four other spores Variants. Among them, F486V exhibited the greatest immune escape.

Tulio de Oliveira said that the Omicron subvariant BA.2 is already more infectious than Omicron, while BA.4 and BA.5 are more infectious than BA.2.

Almost everyone in South Africa has been vaccinated against the COVID-19 or has been infected with the COVID-19. However, the current surge in the number of infected people means that the latest variant is more infectious .

New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems


Helen Rees, a professor at the University of the Witwatersrand in South Africa, said that although Omicron subvariants BA.4 and BA.5 account for about 70% of the confirmed cases in South Africa, and more and more people are currently infected with BA.4 and BA.5 , There has not been a significant increase in deaths or severe illness .

In addition, BA.4 and BA.5 have spread to more than 20 countries around the world in addition to South Africa, but it is unclear whether it will become the new dominant variant globally.

At present, there is no evidence that the infection severity or clinical manifestations of the new strain are different from previous strains, but more conclusions are expected as the research progresses.

WHO chief scientist Sumia Swaminathan also warned earlier that sometimes a virus can change so quickly that it may be able to evade existing immune systems.

Sub-lineages and recombinants of Covid-19 will continue to emerge, and the world must continue to invest in improved tools such as new vaccines.

Only by being prepared can the virus continue to evolve.




New Omicron variants: BA.4 and BA.5 can evade vaccines and immune systems

(source:internet, reference only)

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