Previous colds protect against corona and increase the effectiveness of a vaccination, but only in young people.
Researchers have found out why immunity decreases with age.
Berlin - Why is it that some people can easily cope with an infection with the coronavirus? As a rule, this is due to so-called memory immune cells: They recognize Sars-CoV-2 even though they have never had contact with the virus and set a quick defense reaction in motion. Scientists at the Berlin Charité have already demonstrated this cross-reactivity in 2020. In a new study, the research team is now explaining how the positive findings from then have a negative effect on the vaccination of older people.
In 2020, the researchers attributed the then "surprising" phenomenon of cross immunity to the fact that the memory immune cells then fight the novel coronavirus when they had to deal with other harmless cold viruses with a similar structure in the past.
The results have now been confirmed in a number of studies.
Therefore, previous colds protect a bit against the corona virus
However, the question of how these immune cells influence the course of a later SARS-CoV-2 infection - positively or perhaps even negatively - remained unclear and therefore intensely discussed worldwide. At that time, the Charité scientists assumed a protective effect. “But the opposite could also have been the case. In the case of some viruses, a second infection with a similar virus strain leads to a misdirected immune response, with negative effects on the course of the disease, ”explains Lucie Loyal. She is the first author of the previous and the new study.
Now the Charité researchers have found evidence that supports the assumption of a protective effect.
What is also new is the knowledge that the memory immune cells not only affect the course of the disease after a Covid infection, but also affect the vaccination.
Corona: Reason for "surprisingly quick protective effect" of the vaccination found
With their new study, the Berlin scientists prove that the protective memory immune cells increase antibody formation after a Covid-19 vaccination with the vaccine from Biontech. Means: Those who used to often catch a cold are not only better protected against the coronavirus; the vaccination also lasts longer. Of course, this does not mean that you are definitely protected from SARS-CoV-2 through past harmless colds. "A vaccination is important in any case," emphasizes study director Claudia Giesecke-Thiel.
According to a Charité press release, the new research results explain the “surprisingly quick and very high protective effect” that has been observed, at least in younger people, after the first vaccination.
The different effectiveness of the vaccinations in different age groups could also explain the cross-reaction.
Corona: This is why vaccination protection decreases faster in older people than in boys
In a second part of the study, the scientists were able to demonstrate that cross-immunity decreases with age: Both the number of cross-reacting T cells and their binding strength were lower in older study participants than in younger ones. "This could contribute to the fact that older people become more seriously ill with COVID-19 and that their vaccination protection is often weaker than that of younger people," the scientists conclude.
The authors of the study attribute the decreasing cross-immunity to natural changes in an aging immune system. "The advantage that a harmless coronavirus cold often brings younger people in fighting Sars-CoV-2 and also in building up vaccination protection is unfortunately less in older people," says Thiel and therefore advocates a third booster vaccination in this one more vulnerable population group. This could probably compensate for the weaker immune response and ensure adequate vaccination protection, she explains.