During the development of a vaccine, identification of the correlates of protection is of paramount importance for establishing an objective criterion for the protective performance of the vaccine. However, the ascertainment of correlates of immunity conferred by any vaccine is a difficult task. While conducting a phase three double-blind, cluster-randomized, placebo-controlled trial of a bivalent killed whole-cell oral cholera vaccine in Kolkata, the researchers evaluated the immunogenicity of the vaccine in a subset of participants