Neighborhood-targeted and case-triggered use of a single dose of oral cholera vaccine in an urban setting: Feasibility and vaccine coverage

Introduction In June 2015, a cholera outbreak was declared in Juba, South Sudan. In addition to standard outbreak control measures, oral cholera vaccine (OCV) was proposed. As sufficient doses to cover the at-risk population were unavailable, a campaign using half the standard dosing regimen (one-dose) targeted high-risk neighborhoods and groups including neighbors of suspected cases. Here we report the operational details of this first public health use of a single-dose regimen of OCV and illustrate the feasibility of conducting highly targeted vaccination campaigns in an urban area. Methodology/Principal findings Neighborhoods of the city were prioritized for vaccination based on cumulative attack rates, active transmission and local knowledge of known cholera risk factors. OCV was offered to all persons older than 12 months at 20 fixed sites and to select groups, including neighbors of cholera cases after the main campaign (‘case-triggered’ interventions), through mobile teams. Vaccination coverage was estimated by multi-stage surveys using spatial sampling techniques. 162,377 individuals received a single-dose of OCV in the targeted neighborhoods. In these neighborhoods vaccine coverage was 68.8% (95% Confidence Interval (CI), 64.0–73.7) and was highest among children ages 5–14 years (90.0%, 95% CI 85.7–94.3), with adult men being less likely to be vaccinated than adult women (Relative Risk 0.81, 95% CI: 0.68–0.96). In the case-triggered interventions, each lasting 1–2 days, coverage varied (range: 30–87%) with an average of 51.0% (95% CI 41.7–60.3). Conclusions/Significance Vaccine supply constraints and the complex realities where cholera outbreaks occur may warrant the use of flexible alternative vaccination strategies, including highly-targeted vaccination campaigns and single-dose regimens. We showed that such campaigns are feasible. Additional work is needed to understand how and when to use different strategies to best protect populations against epidemic cholera.
Author summary Oral cholera vaccine (OCV) is becoming part of the standard cholera-control toolkit, although experience in deploying OCV is limited. Adapting vaccination strategies to the global availability of vaccines and the local context (i.e., population movement, security constraints, etc.) is key to maximize the impact of OCV as a cholera-control tool. Here we describe the operational details of the first field use of a single-dose of OCV, which was deployed in a targeted manner, both at high-risk neighborhoods and then to neighbors of suspected cases after the main OCV campaign when sporadic cholera case reports continued. We show that it is feasible to conduct micro- and macro-targeted vaccination campaigns in urban areas like Juba with moderate to high coverage and without social unrest due to vaccinating some groups and not others. Flexible and context-adapted OCV dosing regimens and strategies should be considered in future deployments of the vaccine.