Thread by @ZdenekVrozina

A study comparing the immune system 3 months after COVID-19 and after influenza shows something clear.
SARS-CoV-2 leaves behind a far deeper and longer-lasting immune imprint than seasonal flu.
And the difference isn’t subtle🧵

https://twitter.com/vipintukur/status/1995519758192836668

Researchers used high-dimensional 40-marker CyTOF to map dozens of immune cell types in detail.
The result was so distinct that machine-learning models could accurately classify post-COVID vs post-flu individuals (AUC > 0.95).

The biggest differences appeared in chemokine receptors - the navigation system that tells immune cells where to go.
Post-COVID patients showed markedly increased CXCR3 and CCR6 across multiple lymphocyte populations (T, NK, pDC, monocytes).
This is a unusual and consistent signature.

CXCR3 and CCR6 are not minor markers.
They are the GPS of the immune system.
In post-COVID patients, it is still dialed toward inflamed tissues, especially the lungs.
The body is behaving as if the threat hasn’t fully passed.

This means -
persistent tissue-homing = prolonged low-grade inflammation.
Months after infection, the immune system remains mobilized instead of returning to baseline.

Now the contrast with influenza.
Post-flu patients mainly showed a decrease in CCR4 - a mild, transient pattern consistent with normal recovery.
Influenza does not produce long-lasting chemokine activation.
It does not keep immune cells in a go to tissues mode.
It does not mirror the post-COVID immune state.

Simply -
Influenza leaves behind small footprints.
COVID-19 rewires immune cell trafficking.
The two infections leave completely different immune landscapes.

Most interestingly, the study identified two distinct immunological subgroups within the post-COVID cohort.
The strongest chemokine abnormalities - highest CXCR3/CCR6 levels, most intense tissue-homing - were found in younger individuals.
And this happened even in people with no long COVID symptoms.

That’s a important message.
Feeling recovered ≠ immune system actually returning to normal.
Young immune systems react strongly to SARS-CoV-2, and their hyper-migratory profile persists long after symptoms resolve.
Hidden immunological dysregulation in people who feel perfectly fine.

These differences were not explained by severity of the original infection, hospitalization duration, treatments received (steroids, antivirals, immunomodulators), presence or absence of long COVID
The only factor that distinguished the post-COVID subgroups was age.

This supports the idea that SARS-CoV-2 creates a multisystem, long-lasting immune imprint, particularly visible in chemokine signaling and cell trafficking.
Migration - persistent influx of immune cells into tissues - potential ongoing dysfunction.

Why is COVID-19 so different from flu?
Because SARS-CoV-2 has a much broader tropism. Brain, lungs, heart, vessels, immune cells, kidneys, gut..
This creates a multi-organ immune signature that influenza simply doesn’t generate.

Sum:
COVID-19 leaves the immune system in a state of extended activation and redirected trafficking, still behaving as if it’s hunting the virus.
Influenza does not.
The strongest abnormalities appear in younger individuals - even those who believe they have fully recovered.

This study adds to growing evidence that COVID-19 is not immunologically equivalent to influenza.
The post-infection immune system behaves like it experienced a multisystem viral event, not a simple respiratory illness.

Pérez-Cózar et al., High-Dimensional Immunophenotyping of Post-COVID-19 and Post-Influenza Patients Reveals Persistent and Specific Immune Signatures After Acute Respiratory Infection. Journal of Medical Virology 2025. onlinelibrary.wiley.com/doi/10.1002/jm…

@szupraha (esp Kynčl)
Další důkaz, že tvrzení covid je jako chřipka bylo od začátku nepravdivé.
Rizika jste nepopsali poctivě.
Dlouhodobě vytvářeli dojem, že covid je běžná respirační infekce, což zjevně není.
Výsledkem byla zavádějící komunikace, která poškodila veřejné zdraví.
@ZdravkoOnline @adamvojtech86