University of Geneva study links interferon response to vaccine side effects

Researchers from the University of Geneva have investigated why individuals experience varying levels of side effects following vaccination. A study involving 51 healthy individuals receiving two doses of an mRNA COVID-19 vaccine suggests that the intensity of the immune response is closely linked to interferon activity.

Interferons are proteins produced by cells to alert neighboring cells to a viral presence. The study found that individuals with a more active natural interferon response—potentially due to genetic factors, microbiota, or previous inflammatory episodes—tend to experience more pronounced reactions to the vaccine. These reactions can include local inflammation at the injection site, such as redness or swelling, as well as systemic symptoms like fatigue, fever, or headaches.

Additionally, observations in animal models indicate that a second dose can amplify the activation of innate immune cells, such as monocytes, due to the immunity already acquired from the first dose.