Introducing cholera vaccination in Asia, Africa and Haiti: A meeting report

Feasibility and costs of a targeted cholera vaccination campaign in Ethiopia

Shanchol™, a WHO-prequalified oral cholera vaccine (OCV), has been used to control endemic cholera in Asia, as well as in emergencies and outbreaks elsewhere. The vaccine has not been used by public health systems in cholera-endemic settings of Africa although several outbreak response campaigns have been conducted. Here we present experiences from a mass vaccination campaign in a cholera-endemic setting of Ethiopia in which Shanchol™ was introduced through the public health system. The vaccination site was selected based on cholera cases reported in previous years. Social mobilization involved sensitization of community leaders, household visits, and mass distribution of banners, posters and leaflets. The vaccination was implemented after careful microplanning of logistics and cold chain, manpower, transportation, vaccine supply and supervision and monitoring of adverse events. Vaccine administration was recorded on individual vaccination cards. Vaccine delivery costs were collected and analyzed after vaccination. As there was no experience with Shanchol™ in Ethiopia, a bridging trial was conducted to demonstrate safety and immunogenicity of the vaccine in the local population prior to the mass vaccination. Oral cholera vaccination was conducted in two rounds of four days each in February 2015 and March 2015 in 10 selected villages of Shashemenae rural district of Ethiopia. A total of 62,161 people targeted. 47,137 people (76%) received the first dose, and 40,707 (65%) received two doses. The financial cost of the vaccination campaign was estimated at US $2·60 per dose or US $5·64 per fully immunized person. The cost of vaccine delivery excluding vaccine procurement was $0·68 per dose or $1·48 per fully immunized person. The study demonstrates that mass cholera vaccination administered through the public health system in Ethiopia is feasible, can be implemented through the existing health system at an affordable cost, and the vaccine is acceptable to the community. The lessons from this study are useful for deploying OCV in other African endemic settings through the public health system and may guide future immunization policy decisions.

Efficacy of a bivalent killed whole-cell cholera vaccine over five years: a re-analysis of a cluster-randomized trial

Background

Oral cholera vaccine (OCV) is a feasible tool to prevent or mitigate cholera outbreaks. A better understanding of the vaccine’s efficacy among different age groups and how rapidly its protection wanes could help guide vaccination policy.

Methods

To estimate the level and duration of OCV efficacy, we re-analyzed data from a previously published cluster-randomized, double-blind, placebo controlled trial with five years of follow-up. We used a Cox proportional hazards model and modeled the potentially time-dependent effect of age categories on both vaccine efficacy and risk of infection in the placebo group. In addition, we investigated the impact of an outbreak period on model estimation.

Results

Vaccine efficacy was 38% (95% CI: -2%,62%) for those vaccinated from ages 1 to under 5 years old, 85% (95% CI: 67%,93%) for those 5 to under 15 years, and 69% (95% CI: 49%,81%) for those vaccinated at ages 15 years and older. Among adult vaccinees, efficacy did not appear to wane during the trial, but there was insufficient data to assess the waning of efficacy among child vaccinees.

Conclusions

Through this re-analysis we were able to detect a statistically significant difference in OCV efficacy when the vaccine was administered to children under 5 years old vs. children 5 years and older. The estimated efficacies are more similar to the previously published analysis based on the first two years of follow-up than the analysis based on all five years.

Trial registration

ClinicalTrials.gov identifier NCT00289224

Electronic supplementary material

The online version of this article (10.1186/s12879-018-2981-4) contains supplementary material, which is available to authorized users.