University of Geneva study identifies biological drivers of vaccine side effects

A new study published in the journal Science Translational Medicine has identified biological factors in the human immune system that may explain why individuals react differently to vaccines. While the nocebo effect—where the expectation of negative outcomes increases the likelihood of symptoms—plays a role, researchers found evidence of underlying biological mechanisms driving these variations.

Led by senior author Arnaud Didierlaurent, an associate professor at the University of Geneva, the research team began studying these differences in 2021. The study focused on mRNA COVID-19 vaccines, specifically monitoring 51 previously healthy individuals who received either Moderna’s Spikevax or Pfizer-BioNTech’s Comirnaty.

Previous observations noted that certain patterns exist, such as older individuals often experiencing fewer temporary side effects due to age-related declines in immune function. Understanding these biological drivers is considered crucial, as the potential for adverse reactions remains a significant factor in vaccine hesitancy.