Single-dose cholera vaccine in response to an outbreak in Zambia

Producción CientíficaKilled oral cholera vaccines (OCVs) are part of the standard response package to a cholera outbreak, although the two-dose regimen of vaccines that has been prequalified by the World Health Organization (WHO) poses challenges to timely and efficient reactive vaccination campaigns.1 Recent data suggest that the first dose alone provides short-term protection, similar to that of two doses, which may largely dictate the effect of OCVs during epidemic

The new WHO decision-making framework on vaccine use in acute humanitarian emergencies: MSF experience in Minkaman, South Sudan

Abstract Introduction The main causes of death during population movements can be prevented by addressing the population’s basic needs. In 2013, the World Health Organization (WHO) issued a framework for decision making to help prioritize vaccinations in acute humanitarian emergencies. This article describes MSF’s experience of applying this framework in addition to addressing key population needs in a displacement setting in Minkaman, South Sudan. Case description Military clashes broke out in South Sudan in December 2013. By May 2014, Minkaman, a village in the Lakes State, hosted some 85,000 displaced people. MSF arrived in Minkaman on 28 December 2013 and immediately provided interventions to address the key humanitarian needs (health care, access to drinking water, measles vaccination). The WHO framework was used to identify priority vaccines: those preventing outbreaks (measles, polio, oral cholera vaccine, and vaccine against meningococcal meningitis A (MenAfrivac®)) and those reducing childhood morbidity and mortality (pentavalent vaccine that combines diphtheria, tetanus, whooping cough, hepatitis B, and Haemophilus influenzae type B; pneumococcal vaccine; and rotavirus vaccine). By mid-March, access to primary and secondary health care was ensured, including community health activities and the provision of safe water. Mass vaccination campaigns against measles, polio, cholera, and meningitis had been organized. Vaccination campaigns against the main deadly childhood diseases, however, were not in place owing to lack of authorization by the Ministry of Health (MoH). Conclusions The first field use of the new WHO framework for prioritizing vaccines in acute emergencies is described. Although MSF was unable to implement the full package of priority vaccines because authorization could not be obtained from the MoH, a series of mass vaccination campaigns against key epidemic-prone diseases was successfully implemented within a complex emergency context. Together with covering the population’s basic needs, this might have contributed to reducing mortality levels below the emergency threshold and to the absence of epidemics. For the WHO framework to be used to its full potential it must not only be adapted for field use but, most importantly, national decision makers should be briefed on the framework and its practical implementation

Delayed second dose of oral cholera vaccine administered before high-risk period for cholera transmission: Cholera control strategy in Lusaka, 2016.

BackgroundIn April 2016, an emergency vaccination campaign using one dose of Oral Cholera Vaccine (OCV) was organized in response to a cholera outbreak that started in Lusaka in February 2016. In December 2016, a second round of vaccination was conducted, with the objective of increasing the duration of protection, before the high-risk period for cholera transmission. We assessed vaccination coverage for the first and second rounds of the OCV campaign.MethodsVaccination coverage was estimated after each round from a sample selected from targeted-areas for vaccination using a cross-sectional survey in to establish the vaccination status of the individuals recruited. The study population included all individuals older than 12 months residing in the areas targeted for vaccination. We interviewed 505 randomly selected individuals after the first round and 442 after the second round. Vaccination status was ascertained either by vaccination card or verbal reporting. Households were selected using spatial random sampling.ResultsThe vaccination coverage with two doses was 58.1% (25/43; 95%CI: 42.1-72.9) in children 1-5 years old, 59.5% (69/116; 95%CI: 49.9-68.5) in children 5-15 years old and 19.9% (56/281; 95%CI: 15.4-25.1) in adults above 15 years old. The overall dropout rate was 10.9% (95%CI: 8.1-14.1). Overall, 69.9% (n = 309/442; 95%CI: 65.4-74.1) reported to have received at least one OCV dose.ConclusionsThe areas at highest risk of suffering cholera outbreaks were targeted for vaccination obtaining relatively high vaccine coverage after each round. However, the long delay between doses in areas subject to considerable population movement resulted in many individuals receiving only one OCV dose. Additional vaccination campaigns may be required to sustain protection over time in case of persistence of risk. Further evidence is needed to establish a maximum optimal interval time of a delayed second dose and variations in different settings

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

<div><p>Introduction</p><p>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.</p><p>Methodology/Principal findings</p><p>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).</p><p>Conclusions/Significance</p><p>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.</p></div

Selection of households for inclusion in the neighborhood-targeted vaccine coverage survey.

<p>Selection of households for inclusion in the neighborhood-targeted vaccine coverage survey.</p

Overview of vaccination areas in Juba.

<p>Sub-panel on top left illustrates the case-triggered comprehensive targeted intervention (CTI) approach.</p

Estimated vaccine coverage by age and sex in the neighborhood-targeted campaign.

<p>Red represents women and blue represents men. Lines represent LOESS smoothed estimates of coverage by sex and non-parametric 95% confidence intervals.</p

Population size and vaccine coverage estimates for neighborhood-targeted vaccination campaign.

<p>Population size and vaccine coverage estimates for neighborhood-targeted vaccination campaign.</p

Estimated vaccine coverage by distance to the closest vaccination site in the neighborhood-targeted campaign.

<p>Line represents LOESS smoothed estimates of coverage with non-parametric 95% confidence intervals.</p