Gut microbiome link to post-vaccination fever

Research published in the journal Science suggests a link between gut microbiome composition and the likelihood of experiencing fever or flu-like inflammatory responses following mRNA COVID-19 vaccinations.

Studies involving healthy adults found that individuals who experienced a temperature increase of at least 0.8°C often possessed specific biological features prior to vaccination. These included low-grade intestinal inflammation and gut microbiomes rich in flagellated bacteria from the Lachnospiraceae family. These bacteria produce flagellin, a protein used for movement that activates Toll-like receptor 5 in immune cells, thereby triggering inflammation.

Researchers noted that a steady supply of flagellin may keep the immune system primed, leading to a stronger inflammatory response upon vaccine administration. The findings also indicated that vegetarians and vegans were less likely to experience post-vaccination fever. Importantly, these microbiome characteristics and dietary patterns did not appear to compromise the actual immune protection or antibody response provided by the vaccines. Researchers suggest that dietary interventions to remodel the gut microbiome could potentially be used to reduce adverse reactions and improve vaccine uptake.