Immune Responses to an Oral Cholera Vaccine in Internally Displaced Persons in South Sudan

Abstract

Despite recent large-scale cholera outbreaks, little is known about the immunogenicity of oral cholera vaccines (OCV) in African populations, particularly among those at highest cholera risk. During a 2015 preemptive OCV campaign among internally displaced persons in South Sudan, a year after a large cholera outbreak, we enrolled 37 young children (1–5 years old), 67 older children (6–17 years old) and 101 adults (≥18 years old), who received two doses of OCV (Shanchol) spaced approximately 3 weeks apart. Cholera-specific antibody responses were determined at days 0, 21 and 35 post-immunization. High baseline vibriocidal titers (>80) were observed in 21% of the participants, suggesting recent cholera exposure or vaccination. Among those with titers ≤80, 90% young children, 73% older children and 72% adults seroconverted (≥4 fold titer rise) after the 1st OCV dose; with no additional seroconversion after the 2nd dose. Post-vaccination immunological endpoints did not differ across age groups. Our results indicate Shanchol was immunogenic in this vulnerable population and that a single dose alone may be sufficient to achieve similar short-term immunological responses to the currently licensed two-dose regimen. While we found no evidence of differential response by age, further immunologic and epidemiologic studies are needed.

Long-run effects of early childhood exposure to cholera on final height: Evidence from industrializing Japan

“…This fact is consistent with the evidence that the negative effects of malnutrition are more obvious in early infancy than in the prenatal period and in late infancy ( Neelsen and Stratmann, 2011 , Ampaabeng and Tan, 2013 ). The unclear effects of late infancy exposure would be the acquirement of immunity for cholera in later infancy ( Lyer, Bouhenia, & Rumunu, 2016 ).…”

Dried Blood Spots for Measuring Vibrio cholerae-specific Immune Responses

“…We thus decided to test alternate methodologies for endpoint detection and optimized a drop-plate (or spot-titer) culture method [ 22 ], defining vibriocidal titers as reciprocal of highest dilution of DBS eluates that resulted in reduction in growth (either clumped colonies or serrated margins of growth) as compared to an eluate-free control (confluent bacterial growth). To ensure we were working with samples that were positive for vibriocidal titers, we opted for pre- and post- vaccination DBS samples from volunteers whose vibriocidal titers from matched serum were moderate to high (>160), as determined previously [ 23 ]. Using this method, we could see inhibition in bacterial growth (fewer colonies) at higher eluate concentrations (lower dilutions) and confluent growth at lower eluate concentrations (higher dilutions) ( Fig 1A ).…”

“…Our study has several limitations. In this proof-of-concept study, we selected DBS samples from volunteers immunized with oral cholera vaccine who had serum vibriocidal titers up to 2560 [ 23 ], responses that are expected for OCV, but lower than that usually achieved following natural infection. Validation with samples with a serum vibriocidal titer outside this range is needed, though our experiments with blood spiked with monoclonal antibody shows an ability to detect titers linearly across a large range of titers.…”

The multi-sectorial emergency response to a cholera outbreak in Internally Displaced Persons camps in Borno State, Nigeria, 2017

“…In sum, quantitative studies have analysed humanitarian crises-related cholera intervention measures in isolation focusing on sanitation54 55 in refugee camps, water/hygiene/treatment,56 57 and OCV6–10 58 in IDP camps. Without down playing the rigour of these quantitative studies, excepting Spiegel et al, 11 qualitative studies are needed to explore comprehensive cholera emergency response measures in humanitarian crises including IDPs camps, WASH, case management, surveillance, OCV, coordination, logistics and communication.…”