Brain Abscess Caused by Streptococcus Salivarius Appears in Man After COVID-19 Vaccine
Nikhil Prasad Fact checked by:Thailand Medical News Team Apr 12, 2025 17 hours, 2 minutes ago
Medical News: In a startling medical event that has left researchers puzzled, doctors have reported an extremely rare case of a brain abscess caused by Streptococcus salivarius—a bacterium normally considered harmless—developing in a 63-year-old man shortly after receiving his third COVID-19 vaccination. This unusual case marks the world’s first documented instance of a Streptococcus salivarius brain abscess located in the upper brain region (supra-tentorial area), and the first ever to occur in the wake of an anti-SARS-CoV-2 vaccine.
Brain Abscess Caused by Streptococcus Salivarius Appears in Man After COVID-19 Vaccine
The patient, a North African male with no major health issues prior to the event, had previously received two doses of the ChAdOx1 nCoV-19 vaccine (AstraZeneca), followed by a booster shot of the BNT162b2 vaccine (Pfizer-BioNTech). Within 24 hours of receiving the booster, he began experiencing troubling symptoms including partial paralysis on the left side of his body, facial muscle weakness, vertigo, and balance difficulties. This
Medical News report highlights a concerning and unusual connection between post-vaccine immune responses and rare infections.
When a Friendly Bacterium Turns Dangerous
Initial brain scans (CT and MRI) revealed a sizeable lesion in the right temporo-parietal area of the brain. The lesion had characteristics typical of a brain abscess—a pocket of infection filled with pus. Doctors performed a stereotaxic brain biopsy to extract and examine the abscess, which surprisingly identified Streptococcus salivarius as the culprit. This bacterium, commonly found in the mouth and considered nonpathogenic under normal conditions, had somehow infiltrated the brain tissue and caused a dangerous infection.
Further medical investigations ruled out other common sources of infection, such as endocarditis (heart valve infection) or dental infections, although imaging did show some signs of chronic periodontal disease. A full immunological screening revealed the patient had severe lymphopenia, a condition in which lymphocyte levels in the blood are dangerously low, indicating temporary immunosuppression.
A Second Relapse and the Medical Response
The patient was discharged early but had to return to the hospital just nine days later due to worsening symptoms, including stronger headaches and a progression to full hemiplegia (paralysis on the left side). Follow-up brain scans revealed the abscess had grown in size. A second biopsy showed serous fluid with no bacterial growth, suggesting partial resolution.
Doctors responded with aggressive antibiotic therapy—six weeks of intravenous ceftriaxone—and corticosteroids to control inflammation. In addition, physiotherapy sessions helped the patient slowly regain motor function. Three months later, he showed substantial improvement, with muscle strength returning to 4 out of 5 on the medical scale. Follow-up imaging showed the abscess had fully resolved.
Could COVI
D Vaccines Be a Trigger for Immunosuppression?
The research team, which included experts from the Cheikh Khalifa International University Hospital and Mohammed VI University of Health Sciences in Casablanca, Morocco, along with a contributor from the University of Virginia, USA, explored whether the COVID vaccine may have acted as a biological stressor that temporarily suppressed the immune system. This could have opened a rare opportunity for a typically non-harmful bacterium to cause a life-threatening brain infection.
The study explained that the body's immune response may shift after vaccinations, potentially influencing T cell behavior and cytokine production. For example, some immune responses may lean more toward a Th2 profile (associated with allergy and humoral immunity) rather than the more infection-fighting Th1 response. This shift could lead to a weakened defense against opportunistic infections like Streptococcus salivarius in very rare cases.
A Call for Further Research Not Panic
While the case is remarkable and raises important questions, the researchers caution against jumping to conclusions. They emphasize that no definitive link has been established between COVID-19 vaccines and serious bacterial infections like brain abscesses. However, the incident underscores the need for continued research into how vaccines may occasionally influence immune responses in susceptible individuals.
Conclusion
This rare and unusual case serves as a vital reminder to the global medical community that even commonly benign bacteria like Streptococcus salivarius can, under the right (or rather, wrong) conditions, turn deadly. Though the exact role of the COVID-19 vaccine remains uncertain, the findings highlight the complex relationship between immune system function and vaccination. This patient’s outcome was fortunately positive, thanks to early diagnosis, precise imaging, targeted antibiotic therapy, and careful follow-up. Still, this case should inspire deeper investigations into post-vaccination immune modulation and its potential implications for rare but severe infections.
The study findings were published in the peer-reviewed journal: Clinical Medicine Insights Case Reports
https://journals.sagepub.com/doi/full/10.1177/11795476251325803
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