A study led by Stanford scientists show that oral antibiotics can alter human immune response to seasonal flu jab.

The study included 33 healthy adult participants; of which 22 were studied during the 2014-2015 flu season, and 11 during the 2015-2016 season. The first 22 volunteers had high pre-existing immunity to the strains covered in that season’s flu jab. On the other hand, the group of 11 previously had low immunity to the strains contained in their season’s flu jab.

Half of the participants in each group received a five-day oral course of a broad-spectrum antibiotic regimen (consisting of neomycin, vancomycin, and metronidazole) and then all of them received a seasonal flu jab. The team of researchers analysed the participants’ immune response to the influenza vaccines, as well as the diversity and abundance of the organisms in their gut microbiomes, by studying stool and blood serum samples taken at various times up to one year after vaccination.

In the group of the 2015-2016 season (who had low pre-existing immunity), those who received antibiotics showed hindered immune responses to one of the three influenza virus strains in the vaccine, an H1N1 A/California-specific virus. Therefore, these subjects were less protected against infection with that strain than people who had not received antibiotics.

Additionally, most participants who received antibiotics experienced reduced levels of gut bacteria, and experienced changes to their immune systems that promoted a pro-inflammatory state, similar to a condition seen in older adults who have received influenza vaccines. The researchers of the study think that the pro-inflammatory state is related to the process by which the microbiome regulates the metabolism of bile acid, because with fewer microorganisms, this process is disrupted.


Source: Science Daily