Targeting intestinal microbiota with <i>Bifidobacterium breve</i> and <i>Hafnia alvei</i> 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, <i>Bifidobacterium breve</i> and <i>Hafnia alvei</i>, 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.