{
  "id": 13180602,
  "title": "Gut microbes help set the body's inflammatory response to vaccination",
  "url": "https://urgent.news/2026/10/09/gut-microbes-help-set-the-bodys-inflammatory-response-to-vaccination",
  "topic": "health",
  "section": "Health & Medicine",
  "published": "2026-10-09T18:40:01.000Z",
  "source": {
    "name": "Medical Xpress",
    "slug": "medical-xpress",
    "url": "https://medicalxpress.com/news/2026-10-gut-microbes-body-inflammatory-response.html"
  },
  "original_language": "en",
  "account": "Vaccination is a crucial tool for preventing infectious diseases and safeguarding public health, yet immune responses vary greatly among individuals. Some people experience side effects like fever and flu-like symptoms, while others feel no adverse effects. Researchers from the Max Planck Institute for Biology in Tübingen, Georgia State University, Institut Pasteur in Paris, Inserm, the University of Manitoba, the University of California San Diego, and the Institute for Tropical Medicine at the University of Tübingen have investigated the role of gut microbiome in shaping the inflammatory response to vaccination. Their findings, published in the journal Science, suggest that the composition of gut microbes may predispose individuals to a more inflammatory state, which in turn influences their response to vaccination. The study, dubbed µHEAT (Microbial-Human Ecology and Temperature), recruited healthy young adults who received a SARS-CoV-2 vaccine between 2021 and 2022. Participants provided fecal samples for microbiome analysis and blood samples for immune assessments, while also tracking their temperature in the week leading up to and following vaccination. As anticipated, participants exhibited considerable differences in their temperature responses, with some developing pronounced fevers. Notably, the gut microbiomes of individuals who experienced higher fever responses displayed heightened activity of bacterial motility genes, particularly those encoding for flagellin-producing proteins. Flagellin, a bacterial protein, is recognized as a potential threat by the human immune system, triggering an inflammatory response. Importantly, these microbial differences were present prior to vaccination, indicating that a person's preexisting microbiome could influence their immune tone and subsequent vaccine response. To further explore this connection, researchers conducted a classic microbiome experiment by transferring fecal microbiomes from study participants into immunocompromised mice. These mice were subsequently vaccinated, revealing that those receiving microbiomes from individuals with strong fever responses exhibited more severe inflammation following vaccination. Moreover, the effect appeared to be contingent on the mice's ability to sense microbial flagellin, implying that flagellin contributes to the inflammatory vaccine response. The researchers also examined the role of diet in modulating the gut microbiome and its impact on flagellin production. Participants following plant-based diets tended to have milder fever responses after vaccination. In vitro experiments revealed that certain food additives could stimulate flagellin production by gut microbes. These discoveries suggest that an industrialized diet, rich in processed foods, may foster the growth of flagellated gut bacteria and elevate overall flagellin levels. While the study did not demonstrate that diet alone determines vaccine responses in humans, it indicates that dietary factors can modify a pro-inflammatory microbiome, potentially influencing the strength of the inflammatory vaccine response. Further interventional studies in humans are required to ascertain whether dietary modifications can alter immune reactions to vaccination.",
  "summary": "Vaccination is one of the most important tools for preventing infectious diseases and protecting public health. However, immune responses after vaccination vary dramatically from person to person: If you give many people the exact same vaccine, some will experience side effects such as fever and flulike symptoms while others feel fine.",
  "key_points": [
    "Gut microbiome composition influences inflammatory response to vaccination",
    "Individuals with stronger fever responses have more active flagellin-producing bacteria",
    "Plant-based diets may lead to milder fever responses and altered microbiome"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}