Long Covid and post-Covid symptoms: the most common symptoms and what lies behind them

What is the difference between post-COVID, long-COVID, and post-vaccine syndromes following vaccinations with modified mRNA substances?

Here are short definitions (2-3 lines each) of the terms – based on official or common medical-scientific definitions:

Long COVID syndrome

"Long COVID" refers to the health consequences of a COVID-19 infection when symptoms—whether newly developed or persistent—last for more than approximately four weeks after the acute illness. (Wikipedia+2 Infection control+2)

Post-COVID syndrome

"Post-COVID syndrome" (also "post-COVID-19 condition" or PCC) refers to a condition in which symptoms resulting from a SARS-CoV-2 infection persist or recur at least 12 weeks after the onset of infection—and cannot be explained otherwise. Bavarian Ministry of Health +2 World Health Organization +2

Post-vaccine syndrome (often called "post-vac")

The term "post-vaccine syndrome" is used for persistent symptoms that occur after a COVID-19 vaccination. It is not medically clearly defined and is not subject to a standardized case definition, which /span>significantly complicates its recognition as a vaccine injury. Paul Ehrlich Institute +2Long COVID Platform +2

Vaccination side effect

“Vaccine side effect” refers to health reactions or complaints that occur shortly after vaccination and are considered an undesirable effect of the vaccine — typically short-term and documented within the framework of drug safety. 

What are the most common post-Covid symptoms?

The symptoms can vary greatly. Nevertheless, some recurring patterns are evident worldwide, shared by many sufferers.

1. Fatigue – extreme exhaustion despite rest

What are the symptoms of post-Covid fatigue?

Many people report about:

• persistent fatigue
• Rapid exhaustion: Even climbing one flight of stairs is almost impossible.
• Stress intolerance: Nervous strain and psychological stress lead to overload.
• Difficulties performing everyday activities

What could be behind it?

scientifically discussed:

• Inflammatory processes in the body
• Disorders of energy production (eg, mitochondrial dysfunction)
• Altered immune responses
  
• possible circulatory disorders

These processes can occur in all organs, including the brain, which is why many patients are wrongly diagnosed as mentally ill, even though the psychological symptoms can often be a consequence of inflammatory/circulatory problems in the brain and autonomic nervous system.

2. Brain Fog – Concentration and Memory Problems

Common symptoms of brain fog

• slowed thinking
• Concentration problems
• Word-finding difficulties
• Hypersensitivity to stimuli

Possible mechanisms

Researchers are investigating, among other things:

• inflammatory processes in the nervous system
• disrupted neural pathways
• Reduced oxygen supply due to microclots
  
• autonomic dysregulation

3. Shortness of breath & chest tightness

What could be the reason?

Respiratory problems are among the most common post-Covid symptoms . The following will be discussed:

• Changes in lung function
• Respiratory irritation
• Vascular involvement
• Inflammatory processes in the lungs

Those affected often report shortness of breath at rest or during light exertion.

4. Rapid heartbeat, dizziness & circulatory problems

Many experience symptoms such as:

• Heart palpitations or rapid heartbeat (tachycardia, myocarditis)
• dizziness
• Blood pressure fluctuations
• Circulatory collapse during exertion

Post-Covid and Dysautonomia / POTS

Some of the complaints are related to:

• Autonomic dysfunction
  
• POTS (Postural Tachycardia Syndrome)
  
• unstable heart rate regulation

POTS is a very complex cluster of symptoms that can have individually varying causes. Physicians are therefore faced with a significant challenge in identifying the cause-and-effect relationships. Close, time-consuming, and highly skilled collaboration with the patient is essential.

5. Muscle and joint pain

Pain often occurs in:

• arms and legs
• Back
• chest area
• joints

Possible biological connections

To be discussed:

• persistent inflammation
• altered pain processing
• Muscle metabolism disorders
• Cell destruction processes
  
  

6. Neurological symptoms

In addition to brain fog, those affected report:

• Tingle
• Burn
• Numbness
• Nerve pain

What does the research say?

Study investigations:

• inflammatory reactions in the nervous system
• possible changes in peripheral nerves
• Effects of the immune response

7. Other common complaints

• All inflammatory diseases
• All autoimmune diseases can be partly caused by the virus or the vaccines. Therefore, there has been a sharp increase in Lyme disease, shingles, etc. since 2021.
• Sleep disorders
• Tinnitus
• Gastrointestinal symptoms
• Impairment of sense of smell and taste
• Exercise intolerance (PEM)

What lies behind these post-Covid patterns? – Scientifically discussed mechanisms

Research identifies several possible factors:

1. Immunological dysregulation

Persistent or misdirected immune processes could influence symptoms.

2. Endothelial dysfunction & microclots

Disorders of the inner vessel wall and microclots are the focus of many scientific studies.

3. Inflammatory processes

Several studies are investigating sustained cytokine activity.

4. Autonomic dysfunctions

Dysautonomia can affect the heart, circulatory system, and brain.

5. Disorders of energy metabolism

Mitochondria may work less efficiently.

6. Nervous system & signal transmission

Neuroinflammation and neuronal changes are being investigated.

This list is not exhaustive; for a more comprehensive overview, see, for example, this table of contents: https://www.sound-of-truth.com/downloads/2025-11-23_Leitfaden_IHV.pdf

Conclusion

Post-COVID, long-COVID, and post-VAC are strong>complex sets of symptoms/strong> that can affect all bodily systems and organs. This overview shows which strong>symptoms occur most frequently and which strong>scientific mechanisms/strong> are currently being discussed.

This article does not replace medical advice, but it offers strong>guidance/strong> that many affected individuals are looking for.

Further information

• Anthology (Seeling, 2025) with 40 experts: ………
• Guidelines (Effing&Wacker, 2025) ……