March 24, 2026, 1:14 pm |
Reading time: 5 minutes
Post-vac syndrome is a rare consequence after Covid-19 vaccinations. Those affected often suffer from complaints that affect several body systems at the same time. Researchers from Japan examined 179 cases classified as definitive and found that a large proportion of complaints were concentrated in three main areas. This can help post-vac sufferers to better classify their symptoms.
Fatigue, “brain fog” and pain in muscles and limbs
Table of Contents
- Fatigue, “brain fog” and pain in muscles and limbs
- This is how the researchers proceeded
- Post-Vac Discomfort: Ranking the Most Commonly Affected Areas
- Key findings: High rate of long-term sequelae and severe impairment
- There is no evidence that vaccination was the sole cause of all complaints
- Researchers: Those affected need more support
- Conclusion: Can the result be transferred to Germany?
The study was published by Akinori Fujisawa and colleagues in the journal Scientific Reports.1 The analysis was based on a registry with a total of 279 cases from 14 medical facilities in Japan. For the central evaluations, the researchers focused on 179 cases that were classified as “clinically definitive” in connection with the Covid-19 vaccination. The most common symptom groups were fatigue, diseases of the nervous system (such as “brain fog”) and pain in muscles and limbs.
“Clinically Definitive” Post-Vac Cases:
The PCVS syndrome has not yet been clearly defined. The symptoms are partly similar to those of Long Covid. The researchers established three criteria for definitive cases, all of which had to be met:
1. Before vaccination, the person was either completely symptom-free or had stable health.
2. After the vaccination, the health deteriorated so much that medical help had to be sought.
3. Other possible causes of the symptoms were ruled out and the symptoms persisted for a longer period of time
Also interesting: 8 different paths that Long Covid disease can take
This is how the researchers proceeded
In 179 unique PCVS cases (66.5 percent were women), researchers found a total of 493 health problems or side effects that occurred after vaccination. The range was wide: While some participants only reported one problem, there were patients who were diagnosed with many more different symptoms.
To compare the many different post-vac complaints (e.g. one person described a complaint as a “headache” while another described it as a “headache”), the researchers used a sorting system and sorted the symptoms into three broad categories. The researchers found that most complaints (over 60 percent) focused on three topics:
3 symptom groups dominate the complaints of post-vac patients
- Things like extreme exhaustion (fatigue) or fever were attributed to general illnesses.
- Symptoms such as brain fog, dizziness or headaches have been classified as diseases of the nervous system
- Limb pain or joint problems fell into the category of skeletal muscle and connective tissue diseases
Post-Vac Discomfort: Ranking the Most Commonly Affected Areas
- 29.2 percent of all reported health problems among patients in the study were very severe exhaustion (fatigue), fever or problems walking.
- 22.3 percent were due to “brain fog” (a feeling of mental fog), dizziness and headaches – i.e. problems with the nervous system.
- Pain in the arms and legs, back pain or joint problems accounted for 10.1 percent.
Key findings: High rate of long-term sequelae and severe impairment
The most important finding of the study is that post-vac syndrome (also post-Covid vaccination syndrome or PACVS) can be very persistent. Although around 65 percent of the almost 500 complaints improved (at least partially), almost 30 percent did not change at all. In certain risk groups within the patient group examined, the rate of those who did not recover was even over 60 percent.
About 15 percent of patients had severe adverse symptoms. With 179 patients, that corresponds to around 27 people. They were so sick that, for example, they could not work for a long time or even had to be treated in the clinic.
Late problems, women more commonly affected
Most problems occurred within the first three months after vaccination. What was surprising, however, was that in around 12 percent of those affected the symptoms only began after a year or even later. Overall, women were more likely to be affected by post-vac syndrome (around 67 percent): the average age was 59 years. Six deaths were also recorded during the investigation period.
There is no evidence that vaccination was the sole cause of all complaints
This is an observational study on a small group. The researchers therefore point out that their study cannot prove with certainty that the vaccination was the sole cause of all the symptoms. The authors emphasize that a clear attribution to the vaccination remains difficult, particularly in the case of symptoms that only appeared very late (after more than a year).
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Researchers: Those affected need more support
But what the study makes clear is that there is a small group of people who develop complex, long-lasting symptoms. According to the study, this underlines the global need to create better monitoring systems and specialized care for PCVS patients.
The researchers are therefore very clear that those affected need more support. Many patients would suffer from significant professional restrictions and a high rate of those affected would not recover. Therefore, targeted support for those affected is necessary. The researchers emphasize that PCVS has not yet been medically defined and those affected often have only limited access to health care.
The scientists are specifically calling for these measures
Specifically, the scientists are calling for special treatment networks and framework conditions that are tailored to the diverse and long-lasting complaints of patients. They also call for clear medical guidelines for diagnosis and treatment as well as the creation of compensation systems for those affected. According to the researchers, the results should serve as an important data basis for future vaccination policy.
Conclusion: Can the result be transferred to Germany?
There is a lack of comparable large register data for Germany. The results of the study cannot be statistically transferred to Germany one-to-one, but they do provide important medical information. The study examined only 179 cases from a few Japanese outpatient clinics. This means that there is no information about how common these complaints are overall – neither in Japan nor in Germany. The healthcare system, reporting channels and diagnostic standards also differ.
Here and there, however, the study results can help people suffering from post-vac syndrome to better classify their symptoms. Of course, this does not replace a diagnosis.
