Date Published: August 02, 2017
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Wilfredo R. Matias, Jessica E. Teng, Isabelle J. Hilaire, Jason B. Harris, Molly F. Franke, Louise C. Ivers.
Oral cholera vaccination was used as part of cholera control in Haiti, but the vaccine does not provide complete protection. We conducted secondary data analyses of a vaccine effectiveness study in Haiti to evaluate risk factors for cholera among cholera vaccine recipients. Individuals vaccinated against cholera that presented with acute watery diarrhea and had a stool sample positive for Vibrio cholerae O1 were included as cases. Up to four vaccinated individuals who did not present for treatment of diarrhea were included as controls for each case, and matched by location of residence, enrollment time, and age. We evaluated sociodemographic characteristics and risk factors for cholera. Univariable and multivariable logistic regression were performed to identify risk factors for cholera among vaccinees. Thirty-three vaccine recipients with culture-confirmed cholera were included as cases. One-hundred-and-seventeen of their matched controls reported receiving vaccine and were included as controls. In a multivariable analysis, self-reporting use of branded household water disinfection products as a means of treating water (adjusted relative risk [aRR] = 44.3, 95% confidence interval [CI] = 4.19–468.05, P = 0.002), and reporting having a latrine as the main household toilet (aRR = 4.22, 95% CI = 1.23–14.43, P = 0.02), were independent risk factors for cholera. Self-reporting always treating water (aRR = 0.09, 95% CI = 0.01–0.57, P = 0.01) was associated with protection against cholera. The field effectiveness of water, sanitation, and hygiene interventions used in combination with cholera vaccination in cholera control should be measured and monitored over time to identify and remediate shortcomings, and ensure successful impact on disease control.
Cholera remains a significant cause of morbidity and mortality worldwide, mainly affecting regions that do not have the population-level water, sanitation, and hygiene (WASH) infrastructure that eliminated the disease in Europe and North America over a century ago.1 Oral cholera vaccines (OCVs) are increasingly being deployed as part of a comprehensive approach to prevent cholera globally, and multiple studies have demonstrated their effectiveness.2 However, they do not provide complete protection; vaccinated individuals can still contract the disease.3–5 As such, understanding risk factors for cholera among populations that have been vaccinated against cholera is of critical importance to determine how to design comprehensive integrated programs to eliminate transmission of cholera in the near term.
Our study highlights risk factors for cholera in a high-risk rural population that has received OCV, as well as some, but neither complete nor systematic water and sanitation interventions.19,20 We found that among individuals vaccinated against cholera, consistent water treatment was a key factor in reducing the risk of cholera. Having a latrine as the main household toilet, as opposed to practicing open-air defecation, was a significant risk factor for cholera among this group. Our results also show that those who reported treating water with branded household water disinfection products had an increased risk of cholera. These findings have important implications for policy-makers in Haiti, and other regions where cholera epidemics occur.