A study published in Communications Medicine reports on Apr. 14 that researchers in Australia and Norway have identified protein patterns in blood samples that may help distinguish long COVID from recovery or healthy status, months after initial infection. The research also found that booster vaccinations did not appear to worsen inflammatory responses among those with long COVID.
The findings are significant as they provide new insights into why some people continue to experience symptoms such as fatigue and brain fog for months after contracting SARS-CoV-2, while others recover fully. Understanding these differences is important for improving diagnosis and treatment options for those affected by long COVID.
Researchers analyzed blood samples from participants in Victoria, Australia, dividing them into three groups: healthy individuals with no history of SARS-CoV-2 infection, people who had recovered from COVID-19, and individuals experiencing persistent symptoms classified as long COVID. Samples were collected six to nine months post-infection and before vaccination. Using multiplexed affinity proteomics technology, scientists measured levels of 182 inflammatory and neurology-related proteins along with antibody responses.
Key protein markers identified included interleukin-20 (IL-20), macrophage chemoattractant protein-1 (MCP-1), and neuroblastoma suppressor of tumorigenicity 1 (NBL1). Individuals with long COVID showed elevated IL-20 levels even several months after infection, suggesting ongoing inflammation. Additional proteins such as CLEC10A, TRAIL, and HAGH further distinguished those with lingering symptoms from healthy controls.
The study also examined how immune responses changed following vaccination or reinfection. After receiving a third vaccine dose (booster), all groups demonstrated strong antibody production without an increase in inflammatory markers among the long COVID group. Notably, the immune response to reinfection differed from that observed after initial illness—markers like SIRT2 and 4E-BP1 decreased over time—but the specific pattern of inflammation seen initially was not repeated upon reinfection.
Researchers emphasize that their results support the tolerability of vaccination for people with long COVID since it did not exacerbate inflammation or neurological issues within this cohort. They note that further research involving larger groups is needed to confirm these findings but believe identifying such immune signatures could eventually lead to better diagnostic tools or treatments for those suffering prolonged effects.
