Research conducted by Stanford University scientists found that the use of oral antibiotics weakens the health of the gut microbiome, a complex community of trillions of microbial cells found in each individual. This weakening of the microbiome, in turn, weakens the body’s immune system and alters the response to influenza vaccination.
During the study, all participants received the flu vaccination but only half received antibiotics for a five-day period before receiving the vaccination. Those receiving oral antibiotics had reduced levels of gut bacteria, a hindered response to the vaccine, and experienced higher levels of inflammation—findings that were consistent with previous studies.