Scientists have found immune system dysfunction in most recovered COVID-19 patients even six months after recovery, regardless of the initial severity of the disease.

Australian scientists conducted a large-scale study, during which they conducted a thorough analysis of the long-term effects of COVID-19 on the activity of the immune system. They tracked a wide range of biomarkers and found that immune disorders persist for at least six months after patients recover.

A new study, not yet peer-reviewed or published in a journal, describes the effects of infection on the peripheral immune systems of COVID-19 survivors. Most of the subjects suffered only a mild form of the disease. Blood samples were taken from each subject three times during the six-month study.

Scientists studied the levels of about 130 different immune cells, as well as tracked antibody responses and measured the expression of thousands of different genes associated with immune functions. The results show persistent inflammatory responses and immune dysregulation for six months after recovery.

The study found a significant dysregulation of immune cells that was most severe 12 weeks after infection, but still manifested itself in most cases for six months and possibly even longer.

David Lynn, one of the lead researchers on the project.

The co-author of the study notes that it is possible that the dysregulation is related to the physical symptoms of prolonged COVID-19, however, further research is needed to prove this.

An earlier UK study published in April found persistent immune disorders in hospitalized COVID-19 patients six months after discharge. However, the work of Australian scientists is focusing on various cases of COVID-19, from mild to severe. And one of the biggest surprises for the researchers was the lack of any correlation between the severity of the acute illness and the degree of post-infectious immune dysfunction.

New research is still available on medRxiv.