Targeting intestinal microbiota with Bifidobacterium breve and Hafnia alvei probiotics does not improve response to influenza vaccine in mice.

The intestinal microbiota plays a critical role in shaping host immune responses to pathogens and vaccines. Dextran sulfate sodium-treated mice showed reduced vaccinal response following prime-boost immunization with purified ovalbumin, as confirmed by decreased specific immunoglobulin (Ig)G and IgM, confirming the negative impact of dysbiosis and associated inflammation. Two probiotic strains were selected, Bifidobacterium breve and Hafnia alvei, but none of them showed any enhancement of antibody or T cell responses following prime-boost influenza vaccination in mice. While probiotics remain promising for improving vaccine efficacy, especially in vulnerable populations, further research is needed to identify effective strains and optimize treatment protocols.