Preliminary studies carried out in South Africa, the Netherlands and the United States (USA) reveal that the immune system of those vaccinated or reinfected with SARS-CoV-2 prevents severe cases of covid-19.
Led by specialists from South Africa, the research concluded that a large part of the T cell response, stimulated by vaccination or by previous infections, is maintained in the presence of the Ômicron variant.
According to the researchers, this may be an explanation for the lower number of hospitalizations and deaths than in other waves of the disease.
All studies analyzed lymphocytes, white blood cells capable of remembering a pathogen and eliminating it from the body for months, years, decades, or even throughout life.
The elite of these white blood cells are the so-called “killer lymphocytes” that identify infected cells and kill them. This prevents the virus from prolonging the infection and causing serious illness. To this type of lymphocyte, known as CD8, CD4 is added, which helps to reactivate the immune system in case of a new infection.
Researchers Catherine Riou and Wendy Burgers, from the University of Cape Town, observed the response of “memory” T lymphocytes (which remember how to fight the virus) in 90 people inoculated with Pfizer vaccines (two doses), Johnson & Johnson (one or two doses) or previously infected.
The results – still preliminary since they were not analyzed by independent experts – reveal that the lymphocyte response to Ômicron has an intensity between 70% and 80% compared to the previous variants.
In the United States, the team of immunologist Alessandro Sette analyzed the white cells of 86 people vaccinated with Moderna, Pfizer and Janssen. The results, also preliminary, show that up to 90% of the response remains intact with Ômicron.
In the Netherlands, another preliminary study of 60 healthcare professionals vaccinated with Pfizer, Moderna AstraZeneca or Janssen reveals that the immunity measured by white blood cells against Ômicron is as high as the other variants.
These results contrast with immunity studies carried out so far, which have focused on antibodies. These proteins are produced after infection or vaccination and can prevent the virus from entering cells. Several studies have shown that the effectiveness of antibodies against Ômicron is much lower than that recorded with other variants.
With the large number of Ômicron variant infections reported in many countries, there will be many short-term hospitalizations.
The new data seem to confirm what is being observed in several countries: Ômicron infects people who are vaccinated or already infected, but it is less likely to escape the leukocytes that are still able to identify the cells and eliminate them before they cause serious illness.
This may explain how South Africa had 80% fewer hospitalizations with Ômicron than with previous strains. It is, however, too early to know the real impact of the new SARS-CoV-2 variant on hospitalizations and deaths.
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Lungs
A group of scientists at the University of Hong Kong found that Ômicron replicates 70 times faster than Delta in human airways, but is much slower in infecting lung tissue, which may suggest less seriousness of the disease.
Studies show that SARS-CoV-2 enters cells lining the nose, throat and upper airways differently; therefore, despite being found in large amounts in the airways, the virus concentration is lower in lung tissue.
A team analyzing Ômicron discovered an essential protein found in lung cells, called TMPRSS2, which prevents the new variant from entering and infecting lung cells.
By RTP – Lisbon
