Cholera Vaccine Use Is Associated With a Reduced Risk of Death in Patients With Colorectal Cancer: A Population-Based Study

Background & Aims Cholera toxin can act as a modulator of the immune response with anti-inflammatory effects; it reduces development of colon polyps in mouse models of colorectal cancer (CRC). We performed a population-based study to determine whether, in patients with a diagnosis of CRC, subsequent administration of the cholera vaccine (killed Vibrio cholerae O1 whole cells and recombinant cholera toxin B subunit) affects mortality. Methods We identified patients from the Swedish Cancer Register who were diagnosed with CRC from July 2005 through December 2012. These patients were linked to the Swedish Prescribed Drug Register to retrieve cholera vaccine use. We used Cox regression analysis to calculate the hazard ratio (HR) of death from CRC and overall mortality in patients with post-diagnostic use of cholera vaccine compared with matched controls. Results A total of 175 patients were diagnosed with CRC and given a prescription for the cholera vaccine after their cancer diagnosis. Compared with propensity score-matched controls and adjusted for confounding factors, patients with CRC who received the cholera vaccine had a decreased risk of death from CRC (HR, 0.53; 95% CI, 0.29–0.99) and a decreased risk of death overall (HR, 0.59; 95% CI, 0.37–0.94). The decrease in mortality with cholera vaccination was largely observed, irrespective of patient age or tumor stage at diagnosis or sex. Conclusions In a population-based study, we associated administration of the cholera vaccine after CRC diagnosis with decreased risk of death from CRC and overall mortality.