Achieving coordinated national immunity and cholera elimination in Haiti through vaccination

Abstract

Background Cholera was introduced into Haiti in 2010. Since, there have been over 820,000 reported cases and nearly 10,000 deaths. The year 2019 has seen the lowest reported number of cases since the epidemic began. Oral cholera vaccine (OCV) is safe and effective, but has generally not been seen as a primary tool for cholera elimination due to a limited period of protection and constrained supplies. Regionally, epidemic cholera is contained to the island of Hispaniola. Hence, Haiti may represent a unique opportunity to eliminate cholera by use of OCV. Methods We assess the probability of elimination and the potential health impact of OCV use in Haiti by leveraging simulations from four independent modeling teams. For a 10-year projection period, we compared the impact of five vaccination campaign scenarios, differing in geographic scope, vaccination coverage, and rollout duration to a status quo scenario without vaccination. Teams used common calibration data and assumptions for vaccine efficacy and vaccination scenarios, but all other model features and assumptions were determined independently. Findings A two-department OCV campaign proposed in Haiti's national plan for elimination had less than 50% probability of elimination across models, and only ambitious, nationwide campaigns had a high probability of reaching this goal. Despite their low probability of elimination, two-department campaigns averted a median of 13-58% of infections across models over the five years after the start of vaccination campaigns; a nationwide campaign implemented at the same coverage and rollout duration averted a median of 58-95% of infections across models. Interpretation Despite recent declines in cholera cases in Haiti, bold action is needed to promote elimination of cholera from the region. Large-scale cholera vaccination campaigns in Haiti offer the opportunity to synchronize nationwide immunity, providing near-term protection to the population while improvements to water and sanitation infrastructure create an environment favorable to long-term cholera elimination.

Protection afforded by previous Vibrio cholerae infection against subsequent disease and infection: A review

“…The lower end of these estimates is consistent with another challenge study, in which the majority of participants experienced diarrhea upon their second challenge only 4 to 12 months after the initial challenge [14]. Mathematical models are increasingly used to evaluate and design public health policy [55][56][57][58]. Because model parameters may greatly shape model outcomes, accurate parameter estimates are crucial.…”

Optimizing one-dose and two-dose cholera vaccine allocation in outbreak settings: A modeling study

“…We assumed that protection began immediately after the latest dose received, so that those who are allocated two doses were protected by the first dose until they received their second dose. Vaccination campaigns in Chad and Maela began two weeks after the start of simulation at 50 and 20 cumulative cases respectively, and in Haiti, at the start of simulation with 7300 cumulative cases, consistent with the initiation of surveillance incidence data [26].…”

“…We used a previously developed meta-population model of cholera transmission in Haiti. Each node in the model represents one of the ten administrative departments in Haiti [26]. The departments are connected through a river network and a road network, and within each department, individuals transition through a SEIR framework (Figure 1C).…”

“…We give a brief description here. The decision variable for the optimization problem is the proportion of the total vaccine available allocated to each of four groups (two age groups receiving one or two doses): proportion of population under 5 years old 0.118 [26] Table S4: Description of parameters used in the model of Haiti, unless otherwise specified. (p = person; t = weeks)…”

“…Haiti comprises ten administrative departments, totaling 11 million inhabitants in 2010, with less than 12% under five years old [26]. In 2010 following a catastrophic earthquake, Haiti experienced its first recorded cholera outbreak in at least a century [27].…”