In a study recently published in the journal Allergy, a MedUni Vienna research team found that COVID-19 can lead to significant long-term changes in a person’s immune system, even when cases are mild. The new findings highlight the long-term negative impacts of contracting SARS-CoV-2.SARS-CoV-2 is the virus responsible for COVID-19, a highly infectious disease that emerged in late 2019. The virus primarily spreads through respiratory droplets when an infected person coughs, sneezes, or talks. Symptoms of COVID-19 can range from mild to severe and include fever, cough, and difficulty breathing, with some individuals experiencing fatigue, body aches, loss of taste or smell, and gastrointestinal (GI) distress. The significance of SARS-CoV-2 lies in its rapid global spread, leading to widespread illness, significant mortality, and profound impacts on healthcare systems, economies, and daily life. Efforts to control the pandemic have included public health measures like social distancing, mask-wearing, and vaccination campaigns. However, the virus seems to be here to stay.As part of the latest study, the team led by first authors Bernhard Kratzer and Pia Gattinger and principal investigators Rudolf Valenta and Winfried Pickl (all from MedUni Vienna's Center for Pathophysiology, Infectiology and Immunology) took a look at immune parameters in 133 people who had recovered from COVID-19 and 98 others who hadn’t experienced the virus. The number and composition of various immune cells as well as cytokines and growth factors in the blood were examined in the recovered patients at 10 weeks and again at 10 months after their initial diagnosis.

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As no COVID-19 vaccines were available during the observational time period in 2020, all participants were, by default, unvaccinated. This allowed the study authors to investigate the long-term effects of SARS-CoV-2 infection without factoring in vaccination rates and the impact of increasing immunity to the virus.The team found that ten weeks after the infection, the recovering COVID-19 patients showed clear signs of immune activation of both T and B cells, in contrast to the subjects who hadn’t contracted the virus. Compared with patient samples collected ten months after the initial COVID-19 infection, revealed unexpected results."Even after mild disease progression, we found a significant reduction of immune cells in the blood," said co-author Winfried Pickl. For COVID-19 recovering subjects, this meant that their immune system may no longer be responding optimally to new threats of infection and disease.Overall, the team discovered that an infection and the resulting long-term bone marrow dysfunction in patients who had contracted the virus resulted in long-term health consequences impacting their ability to fight off future health hazards."Our results provide a possible explanation that certain long-term consequences of COVID-19 could be related to the damage to the cellular immune system caused by SARS-CoV-2 and the apparently reduced maturation and/or emigration of immune cells from the bone marrow," both Pickl and Rudolf Valenta stated.These concerning results prompt the need for more research to more fully understand the long-term, perhaps permanent, impact of the virus on public health.

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