Study Finds Long-Term Immune Changes Linked to COVID-19

In a study recently published in the renowned journal "Allergy", a MedUni Vienna research team showed that COVID-19 leads to considerable long-term changes in the immune system, even in mild cases.

COVID-19, caused by the SARS-CoV-2 virus, significantly impacts the body's immune system. Even after mild cases, the virus can lead to a lasting reduction in immune cells and a drop in specific antibodies. This weakens the immune system's ability to respond to new infections. Additionally, changes in cytokines and growth factors indicate a lingering inflammatory response. These effects suggest that COVID-19 can cause long-term immune system impairments, potentially contributing to prolonged health issues such as Long-COVID.

In the study, researchers looked at important immune markers in 133 people who had recovered from COVID-19 and 98 people who had never had the virus. They analyzed the number and types of various immune cells, as well as cytokines and growth factors in the blood, which are crucial for regulating cell growth. The recovered patients were tested ten weeks and ten months after their initial infection. Since there were no COVID-19 vaccines available in 2020 during the study period, all participants remained unvaccinated. This allowed the researchers to examine the long-term effects of the SARS-CoV-2 infection without any influence from vaccines.

The study also found that cytokines and growth factors in the blood of recovered patients were typical of those seen after an acute inflammatory process. When comparing samples from patients taken ten months after recovering from COVID-19, researchers noticed an unexpected pattern. Even after mild cases, there was a significant reduction of immune cells in the blood.

Additionally, there was a notable drop in SARS-CoV-2-specific antibodies and a surprising change in growth factor patterns in the blood.

This suggested that the immune systems of those who had COVID-19 might not respond as effectively to new challenges, possibly explaining some long-term effects of the virus, such as Long-COVID. Researchers believe that these long-term impacts are likely due to the infection causing prolonged impairment of the bone marrow, which is crucial for producing immune cells.

Reference: Kratzer, B., et al. (2024) Differential decline of SARS-CoV-2-specific antibody levels, innate and adaptive immune cells, and shift of Th1/inflammatory to Th2 serum cytokine levels long after first COVID-19. Allergy. doi.org/10.1111/all.16210.