Gut microbiome may explain fever after vaccination

Researchers at the Max Planck Institute for Biology Tübingen found that stronger post-vaccine fevers are linked to gut bacteria producing the protein flagellin. Transferring participants' microbiomes into mice reproduced stronger inflammatory responses after vaccination.

• Participants with stronger fevers had elevated inflammation before vaccination
• Flagellin from bacterial flagella is sensed by the immune system as a danger signal
• Mice given microbiomes from high-fever participants showed stronger inflammation
• Plant-based diets were associated with milder fever responses