Compositions and methods are described for inducing an immune response against extra-intestinal pathogenic Escherichia coli (ExPEC) to thereby provide immune protection against diseases associated with ExPEC. In particular, compositions and methods are described for using conjugates of E. coli polysaccharide antigens O25B, O1A, O2, and O6A covalently bound to a detoxified exotoxin A of Pseudomonas aeruginosa (EPA) carrier protein as vaccines for the prevention of invasive ExPEC disease caused by ExPEC serotypes O1A, O2, O6A and O25B.
