Thursday, January 07, 2021
Immune memory fluctuates
How long are you immune after Corona?
So far it has been rather unclear how long one is immune to renewed infection after a corona infection. With data from US researchers, the period can now be narrowed down more precisely for the first time. However, there can be significant deviations.
Regardless of the concern you should have about a corona infection, it has one advantage – the body comes into contact with the virus and can form an immune response to it. However, until now it was very unclear how long the resulting immunization against the virus lasts. A US study is now presenting new data on this. According to this, important components of the immune memory can be detected in most patients eight months after surviving an infection.
The research team from the La Jolla Institute for Immunology followed the immune events in 188 Covid-19 patients over eight months for their study, which was published in Science magazine. The 80 men and 108 women came from California or New York. Most had a “mild” history of Covid-19 that did not require hospitalization. Only 7 percent of the subjects were treated in the hospital, some also in the intensive care unit.
Using blood samples, the scientists determined the content of the antibodies specific for the spike protein of Sars-CoV-2, of B memory cells, of CD4 + T cells and of CD8 + T memory cells. These are four components of what is known as immune memory. B memory cells keep the “building instructions” for the virus-specific antibodies, so to speak, and enable the rapid production of large quantities of these antibodies when they come into contact with the virus. CD4 + and CD8 + T memory cells also “remember” certain proteins or protein parts of the virus and, in the event of a second infection, promote, among other things, the activation of T killer cells and T helper cells, which then release antiviral messenger substances.
Good immune memory
95 percent of the patients in the study carried at least three of these components five to eight months after surviving the infection. The amount of neutralizing antibodies decreased slowly over time in most of the test subjects, in some, for example, the virus-specific immunoglobulin G antibodies were only detectable in small amounts after just under three months.
However, 90 percent of the patients were still tested positive for neutralizing antibodies against Sars-CoV-2 after six to eight months, report Jennifer Dan and her team. The defense and memory cells are therefore usually preserved for a long time. The memory B cells increased even further in the four months after infection and then remained at a high level. “Based on our observations, B-cell memory is robust and likely to be long-lasting,” the researchers note.
The CD4 + T memory cells could also be detected in 92 percent of the test subjects six months after the infection. The virus-specific CD8 + T cells, however, decrease faster. After one month they were still detectable in 70 percent of the participants, after six months only in half. Nevertheless, the researchers assume that the immune protection against Sars-CoV-2 lasts for at least six to eight months in very many people. In her opinion, during this time you are at least protected against severe courses of Covid-19.
The doctors and scientists suspect that their results can also be transferred to vaccinations. But you only know for sure if you have collected similar data. However, the study also shows how different the immune response can be, which is then also reflected in the immune memory. In the study, there was a proportion of less than five percent of the test persons in whom this immune memory was rather weak. The scientists write that they could become prone to re-infection again relatively quickly.