# Max Planck Institute Links Gut Flagellin to Vaccine Fever in Human and Mouse Studies

- Published: 2026-11-07 09:51 UTC
- Section: Life & Health › Medicine
- Tags: gut microbiome, vaccine fever, Max Planck Institute, flagellin, inflammatory response, diet and microbiome
- URL: https://realtech.media/news/rt-d2acc871e1c98d17c89c6785_max_planck_institute/

**Researchers found that gut microbes producing bacterial flagellin correlate with post-vaccination fever, confirming the causal link in gnotobiotic mice.**

![Max Planck Institute Links Gut Flagellin to Vaccine Fever in Human and Mouse Studies](https://realtech.media/media/2026/11/19675eb9c26b1541.jpg)
*lomazoma.com*

An international research team led by the Max Planck Institute for Biology Tübingen has identified a link between the baseline gut microbiome and post-vaccination fever, according to scitechdaily.com [1]. In a study of healthy young adults receiving SARS-CoV-2 vaccines during 2021 and 2022, participants who developed substantial fevers exhibited elevated baseline inflammation and greater bacterial gene activity related to flagella prior to injection [1].

To establish causality beyond human observational data, the authors transferred fecal microbiota from trial participants into germ-free mice lacking native intestinal microbes [1]. Upon subsequent vaccination, animals receiving microbiota from high-fever individuals developed stronger inflammatory responses than mice inoculated with microbes from low-fever donors [1]. The researchers noted that this elevated response depended directly on the hosts' ability to sense flagellin, the primary structural protein of bacterial flagella [1].

## Microbial Flagellin and Baseline Inflammation

Flagella are whip-like appendages used for bacterial motility, synthesized from flagellin proteins [1]. Because pathogenic organisms like Salmonella express similar structures, the host immune system recognizes flagellin as an innate danger signal, which primes systemic inflammatory tone [1]. Participants experiencing marked febrile reactions demonstrated heightened expression of microbial motility genes and increased inflammation markers in both fecal and blood samples prior to vaccination [1].

## Dietary Influences and Experimental Models

Observations within the human cohort showed that individuals consuming plant-based diets tended to exhibit weaker febrile reactions [1]. In laboratory settings, specific food additives boosted bacterial flagellin production in vitro, according to researchers from Institut Pasteur [1]. Furthermore, experiments conducted at Georgia State University revealed that administering a high-fat Western-style diet to mice heightened inflammatory responses following vaccination [1]. The authors emphasized that human interventional trials are required to establish whether direct dietary changes can modify microbial flagellin production and mitigate vaccine-induced fever [1].

## Sources

1. [scitechdaily.com](https://scitechdaily.com/why-do-some-people-get-fevers-after-vaccines-scientists-may-have-found-the-answer/)
2. [lomazoma.com](https://lomazoma.com/darmmikrobiom-und-ernaehrung-koennen-fieberreaktion-nach-impfungen-beeinflussen-news-deutsches-aerzteblatt)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-d2acc871e1c98d17c89c6785_max_planck_institute/