Recent studies reveal indicators linked to blood clotting, immunity, and microvessels, which may help explain the persistence of fatigue, brain fog, and shortness of breath in some COVID survivors, but reaching a definitive treatment still requires further research.
Years after contracting the coronavirus, some survivors continue to suffer from persistent symptoms that affect their daily lives, most notably extreme fatigue, shortness of breath, and impaired concentration and memory, in the absence of a clear explanation for all cases.
Recent studies suggest a potential link between these symptoms and changes in blood clotting, the immune system, and microvessels, after researchers observed microscopic protein aggregates and signs of cellular and immune disorders in some patients with long COVID.
In a study published in the Journal of Medical Virology in October 2025, researchers observed an increase in the number and size of protein aggregates in patients, along with their association with the activity of immune networks released by white blood cells known as neutrophils.
The results suggest that abnormal immune activity may contribute to the persistence of some clotting-related changes, but the study did not prove that these mechanisms are the direct cause of the symptoms.
A preliminary study published on the medRxiv platform in August 2026 also showed that blood samples from some patients were faster to initiate clotting and form clots compared to samples from healthy individuals. However, the study is limited in size and has not yet undergone peer review.
Research has extended to microvessels; a study published in the journal Microcirculation in September 2026 observed impaired vascular responses and delayed recovery after blood flow restoration in long COVID patients, coinciding with changes in indicators of chemical balance within cells.
In another study published online in July 2026 in The Journal of Allergy and Clinical Immunology, researchers discovered changes in certain immune and endothelial cells, along with signs of cellular stress and aggregates containing platelets and immune cells.
These findings may help explain some symptoms, such as extreme fatigue, brain fog, and shortness of breath, but these symptoms may arise from multiple mechanisms including inflammation, sleep disorders, autonomic nervous system issues, and metabolic changes.
Researchers warn against confusing the discovery of protein aggregates in blood samples with proof of clots blocking blood vessels inside the body, as the relationship between these aggregates and symptoms still requires further verification.
Furthermore, studies have not yet proven that the use of anticoagulants or plasma purification treats long COVID, and there are no approved diagnostic tests based on these indicators alone.
Experts emphasize that the crucial step is to conduct larger studies and controlled clinical trials to determine whether these changes actually cause the symptoms, and whether targeting them leads to patient improvement.
Thus, the new discoveries open promising paths for understanding long COVID, but they do not yet provide a definitive explanation for the disease or a proven treatment for it.
