Antibodies generated by infection with the original version of Ômicron – BA.1, responsible for the Covid-19 wave in January – do not protect against the sub-variants BA.4 and BA.5, which have become widespread in Brazil. The conclusion is a study conducted by researchers at Peking University in Beijing, China, published last Friday in the scientific journal Nature.
According to an analysis conducted by Instituto Todos pela Saúde (ITpS), made with data from Dasa and DB Molecular laboratories, the proportion of probable cases of BA.4 and BA.5 in the country increased from 10.4% to 44%. The other samples are from the BA.2 subline. At the same time, the positivity of Covid-19 – the percentage of tests with a positive result – increased from 23.6% to 42.3%.
“The increase in a short time shows that these variants are more transferable because they are able to overcome the variant that prevailed at the time, in this case Omicron BA.2. The unprecedented fact is that BA.4 and BA.5 variants are derived from BA.2 and this is the first time this is happening in the pandemic: a VOC (variant of concern) derived from a predecessor VOC that caused a new wave.Until then this had not happened.The previous waves were caused by VOCs not derived from the previous ones, “said José Eduardo Levi, a virologist at Dasa.
However, ITpS warned that the impact of current versions of the disease tends to be lower than the January wave, caused by BA.1, due to vaccination coverage, which is still expected to protect against the most severe forms of Covid -19. 19.
In May, a study by scientists in South Africa, the first place to identify the new sub-strains, had already considered their ability to avoid antibodies from previous Covid-19 infections, but with less ability to thrive in the blood of vaccinated humans.
In addition to the ability of the new subvariants to evade immunity, another reason for the high re-infection rate is the response generated by BA.1. According to a study by researchers at Imperial College London, England, published in the journal Science, Omicron infection provided an immune boost against earlier variants (Alpha, Beta, Gamma, Delta and the original strain), but little effect against Omicron itself.
Reinfection at BA.4 and BA.5
In the new Chinese study, researchers analyzed the response of antibodies generated by BA.1, with and without vaccination, to combat BA.4, BA.5 and BA.2.12.1 – the latter being prevalent in the United States. They found that the mutations in the new subvariants manage to escape protection and therefore cause new infections.
“Unlike when Ômicron first appeared, Ômicron sublines can now target humoral immunity induced by Ômicron itself, such as post-vaccination infection. (…) These phenomena represent a major challenge to the flock immunity currently established through vaccination and infection with BA.1 and BA.2 They also suggest that the Omicron BA.1-based vaccine (currently under development by Pfizer and Moderna) may not be the ideal antigen to induce broad-spectrum protection against new Omicron sublines, ”wrote the Chinese researchers.
This month, Moderna, the pharmaceutical company responsible for one of the world’s vaccines against Covid-19, announced that the specific version of the immunizer under development for Ômicron induced eight times more antibodies to the variant than the booster with the current formulation. Laboratory chief executive Stéphane Bancel said he expected the new application would be available in September. However, the new vaccine is based on BA.1, which Chinese researchers believe may limit protection against the new strains.
most symptomatic infection
In addition, preliminary data from a study conducted by scientists at the University of Tokyo, Japan, not yet peer-reviewed, show that the subvariants BA.4, BA.5 and BA.2.12.1 may have regained the ability to infect cells. of the lung, making them more pathogenic and similar to early Covid-19 variants such as Delta.
Researchers believe that BA.1 and BA.2 – early subvariants of Ômicron – cause a milder condition by infecting the upper respiratory tract instead of the lungs. The results of the Japanese study indicate that BA.4 and BA.5 may no longer have this behavior and generate more severe symptoms.
However, experts point out that vaccination is still able to prevent the most serious cases and deaths due to the disease. Therefore, they believe that while it may escape previous immunity and cause more serious infections, the new underlines should not affect the health systems as much as previous waves of Covid-19 or pose an equal threat to the immunized.
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