Even mild course

Corona infection causes permanent damage to the immune system

A team of researchers from MedUni Vienna investigated the long-term consequences of an infection with SARS-CoV-2. The scientists found that Covid-19 disease leads to considerable long-term changes in the immune system, even in mild cases.

The study, which began in 2020, involved 133 people who had recovered from Covid-19 and 98 people without such an infection. The number and composition of various immune cells and the growth factors in the blood of the recovered patients were analyzed ten weeks and ten months after their illness, which play a decisive role in the regulation of cell growth, among other things. As there were no Covid-19 vaccines available at the start of the research work, all participants were unvaccinated.

Significant reduction in immune cells
Not entirely unexpectedly, ten weeks after infection, the recovered patients showed signs of inflammation and immune activation in both T and B cells as well as growth factors in the blood, in contrast to healthy volunteers. However, the following was unexpected: "Even after mild courses of the disease, we found a significant reduction in immune cells in the blood," reports Prof. Dr. Winfried Pickl, one of the two study leaders from MedUni Vienna's Center for Pathophysiology, Infectiology and Immunology. 

In addition, the well-known drop in SARS-CoV-2-specific antibodies and an astonishing change in growth factor patterns in the blood were observed. According to the researchers, the long-term consequences of the disease are presumably caused by the infection and the resulting long-term impairment of bone marrow function (central production site of immune cells). 

Possible explanation for Long Covid
For people who have recovered from Covid-19, this means that their immune system may no longer respond optimally, which could provide an explanation for Long Covid. In any case, the results of the study form the basis for further research to gain a better understanding of the mechanisms underlying long Covid.