Coronavirus: The immune system of vaccinated and infected resists to omicron | Science

The immune system of people who have been vaccinated or have already had a coronavirus infection eliminates the omicron variant before it makes them seriously ill, according to several preliminary studies carried out in South Africa, the United States and the Netherlands. The authors argue that this could explain why in several countries omicron is producing fewer hospitalizations and deaths than in other waves.

All the works analyze lymphocytes, white blood cells capable of remembering a pathogen and sweeping it from the body for months, years, decades, even throughout life.

The elite of these white blood cells are made up of lymphocytes assassins They identify infected cells and ruthlessly kill them. This prevents a virus from prolonging the infection and can cause serious illness. To this type of lymphocytes, known as CD8, are added the CD4 that help to reactivate the immune system in the event of a new infection.

The team of virologist Wendy Burgers from the University of Cape Town (South Africa) has analyzed the levels of these two types of lymphocytes in the blood of 90 patients vaccinated with Pfizer or Janssen – or who had had previous disease. Your results —As yet preliminary as they have not been analyzed by independent experts— show that the response of lymphocytes against omicron has an intensity of between 70% and 80% compared to that of previous variants. The team also analyzed plasma from 19 hospitalized omicron-infected patients. All of them were unvaccinated and had not had COVID before. The results show that its lymphocyte response is as effective as that of those admitted by other previous variants.

In the United States, the immunologist’s team Alessandro Sette has analyzed the white blood cells of 86 people vaccinated with Moderna, Pfizer and Janssen. Their preliminary results show that up to 80% of the response remains intact against omicron. “These results mean that up to 80% of our police officers continue to patrol the agency,” explains Sette to EL PAÍS. “We still don’t know what level of protection is sufficient. It depends on whether we are referring to a contagion or a serious disease. Probably this level of lymphocytes does not prevent the first, but it does prevent the second “, details the researcher at the La Joya Institute of Immunology.

In Holland another preliminary study focused on 60 doctors and healthcare workers vaccinated with Pfizer, Moderna, Astra Zeneca or Janssen. The results show that the immunity mediated by white blood cells against omicron is as high as against other variants.

These results are in contrast to immunity studies conducted 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 the antibodies against omicron is much lower than that registered in other waves.

With the huge number of cases registered in many countries there will be many hospitalizations in a short period of time

Wendy Burgers, virologa

The new published data seem to fit in with what is being observed in many countries: omicron is capable of infecting vaccinated people or people who had already been infected, but it is less able to escape the white blood cells that are still able to identify infected cells and eliminate them. before it can cause serious illness in most cases. This would explain why countries like South Africa have detected up to 80% fewer hospitalizations in the omicron wave than in the previous ones. In any case, it is too early to know the real impact of the omicron wave on hospitalizations and deaths.

The South African analysis is based on infections registered during the first half of December, which does not show what was seen during this entire wave. There is no more recent data. “We were exhausted from working 16 hours a day and also the equipment was depleted by omicron infections,” says Burgers. “We had to stop two weeks and we hope to start over the next one,” explains the South African researcher, in whose country the curfew has been lifted after apparently overcoming the peak of this new wave.

Many experts already consider omicron the virus with the most spread in history. “In South Africa, mortality and disease severity have been lower with omicron,” Burgers explains. “But with the enormous number of cases registered in many countries, many hospitalizations are to be expected in a very short period of time in which many health workers will be on sick leave due to infection. The situation is very serious ”, he warns.

Much of what happens depends on the level of vaccination. The studies mentioned also show that a third dose of vaccine causes antibody levels to return to high and the ability to avoid infection is restored. “It is still too early to provide conclusive data on the severity of omicron infection in different parts of the world,” says Andrew Redd, a researcher at the US National Institute of Infectious Diseases. His team was one of the first to publish that the ability of lymphocytes to defeat omicron it is “practically intact” despite the mutations it accumulates. “For now the only thing we can say is that getting vaccinated is the best thing anyone can do to avoid getting sick with omicron or any other variant. Everyone should get vaccinated as soon as possible and receive a booster dose if applicable ”, he highlights.

Marcos López-Hoyos, president of the Spanish Society of Immunology, views all these data with cautious optimism. “The infection is triggered because the capacity of the antibodies that neutralize the virus is failing, which barely reaches 20%,” he highlights. “On the other hand, the lymphocytes analyzed in these studies are capable of preventing serious disease. With a protection of between 70% and 80%, the vast majority of those infected will not suffer a serious disease. In addition, there is a new study that shows that the third dose not only increases the level of antibodies, but also that of CD4 lymphocytes, ″ he adds.

These results are similar to those seen with other dangerous variants.Early work showed that the coronavirus escaped antibodies generated by vaccines or infection, but data on white blood cells later indicated that immunity against severe disease remained largely intact. .

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