The O‐specific polysaccharide linked to the core (OSPc) portion of the lipopolysaccharide (LPS) of Gram‐negative bacteria is an ideal antigenic component of a cholera vaccine. This work describes the isolation and purification of the OSPc of Vibrio cholerae O139 in the purest state reported to date. After characterizing the OSPc by NMR spectroscopy and mass spectrometry, the missing structural details in the core were elucidated. The purified OSPc was then conjugated to carrier protein by squaric acid chemistry. The conjugate showed immunoreactivity with sera from patients in Bangladesh recovering from cholera caused by V. cholera O139, but not O1. More information can be found in the Full Paper by P. Xu et al. on page 12946.