WHO has recently labeled sepsis as a most urgent unmet medical need With 30 million cases and 8 million deaths yearly (including 3 million children) sepsis is indeed very prevalent The infectious bacterial agent is unpredictable, but mostly belongs to a shortlist of about 10 species, and bacterial septic pneumonias and peritonitis share a number of overlapping contaminants In a mouse model of polymicrobial septic peritonitis, we have developed a broadly and long-acting vaccine, based on vaccination of mice with cecal contents and an adjuvans The immune protection appears to depend on serum components, likely antibodies We believe that developing a broad vaccination strategy to protect against a broad panel of infectious agents is an interesting strategy to persue To identify the major antigens and relevant bacterial species in the current first version of vaccine and to develop an improved vaccine that is reproducible and known in composition, we will develop a differential vaccination strategy, based on 5 different populations of donors which range from mice without cecal contents (germfree mice) to mice with a very rich cecal commensal flora content The increased vaccination potential will form the basis to identify the antigens and antigenic bacteria via three strategies, involving FACS sorting/metagenomics, Mass Spec and phage display libraries The major result of the project will be a newly composed and broadly protecting, safe vaccine against sepsis