Eff ectiveness of one dose of oral cholera vaccine in response to an outbreak: a case-cohort study

Background Oral cholera vaccines represent a new eff ective tool to fi ght cholera and are licensed as two-dose regimens with 2–4 weeks between doses. Evidence from previous studies suggests that a single dose of oral cholera vaccine might provide substantial direct protection against cholera. During a cholera outbreak in May, 2015, in Juba, South Sudan, the Ministry of Health, Médecins Sans Frontières, and partners engaged in the fi rst fi eld deployment of a single dose of oral cholera vaccine to enhance the outbreak response. We did a vaccine eff ectiveness study in conjunction with this large public health intervention. Methods We did a case-cohort study, combining information on the vaccination status and disease outcomes from a random cohort recruited from throughout the city of Juba with that from all the cases detected. Eligible cases were those aged 1 year or older on the fi rst day of the vaccination campaign who sought care for diarrhoea at all three cholera treatment centres and seven rehydration posts throughout Juba. Confi rmed cases were suspected cases who tested positive to PCR for Vibrio cholerae O1. We estimated the short-term protection (direct and indirect) conferred by one dose of cholera vaccine (Shanchol, Shantha Biotechnics, Hyderabad, India). Findings Between Aug 9, 2015, and Sept 29, 2015, we enrolled 87 individuals with suspected cholera, and an 898-person cohort from throughout Juba. Of the 87 individuals with suspected cholera, 34 were classifi ed as cholera positive, 52 as cholera negative, and one had indeterminate results. Of the 858 cohort members who completed a follow-up visit, none developed clinical cholera during follow-up. The unadjusted single-dose vaccine eff ectiveness was 80·2% (95% CI 61·5–100·0) and after adjusting for potential confounders was 87·3% (70·2–100·0). Interpretation One dose of Shanchol was eff ective in preventing medically attended cholera in this study. These results support the use of a single-dose strategy in outbreaks in similar epidemiological settings

Epidemiological description of a protracted cholera outbreak in Tonj East and Tonj North counties, former Warrap State, South Sudan, May-Oct 2017

Abstract Background On 18th May 2017, State Ministry of Health of former Warrap State received a report from Tonj East County of an outbreak of acute watery diarrhoea and vomiting in Makuac payam. We conducted this investigation to confirm the causative organism and describe the epidemiology of the outbreak in order to support evidence-based control measures. Methods We defined a suspected case as a resident of Tonj East or Tonj North County with sudden onset of acute watery diarrhoea and vomiting between May 1 and October 15, 2017. A probable case was defined as a suspected case with a positive rapid test for Vibrio cholerae; a confirmed case was a probable case with a positive stool culture for V. cholerae. We conducted systematic case finding by visiting health facilities and villages in the affected payams. We reviewed patient records from 1 May 2017 to 15 October 2017, to identify suspected cholera case-patients. We conducted a descriptive epidemiologic study, examining the distribution of the cases. We computed the attack rates by age, sex, and payam of residence. Case fatality rate was calculated as the ratio of the total number of suspected cholera death to the total number of cholera case-patients. We conducted an oral cholera vaccination campaign after the peak of the outbreak to control and prevent the spread to other payams. Results We identified 1451 suspected cholera cases between May and October 2017. Of these, 81% (21/26) had a positive rapid diagnostic test for V. cholerae; out of the 16 rectal swabs transported to the National Public Laboratory, 88% (14/16) were confirmed to be V. cholerae O1 serotype Inaba. The epidemic curve shows continuous common source outbreak with several peaks. The mean age of the case-patients was 24 years (Range: 0.2-75y). The clinical presentations of the case-patients were consistent with cholera. Males had an attack rate of 9.9/10000. The highest attack rate was in ≥30y (14 per 10,000). Among the six payams affected, Makuac had the highest attack rate of 3/100. The case fatality rate (CFR) was 3.0% (44/1451). Paliang and Wunlit had an oral cholera vaccination coverage of ≥100%, while 4 payams had a vaccination coverage of < 90%. Conclusion This was a continuous common source cholera outbreak caused by V. cholerae 01 sero type Inaba. We recommended strengthening of the surveillance system to improve early detection and effective response

Cholera Rapid Test with Enrichment Step Has Diagnostic Performance Equivalent to Culture.

Cholera rapid diagnostic tests (RDT) could play a central role in outbreak detection and surveillance in low-resource settings, but their modest performance has hindered their broad adoption. The addition of an enrichment step may improve test specificity. We describe the results of a prospective diagnostic evaluation of the Crystal VC RDT (Span Diagnostics, India) with enrichment step and of culture, each compared to polymerase chain reaction (PCR), during a cholera outbreak in South Sudan. RDTs were performed on alkaline peptone water inoculated with stool and incubated for 4-6 hours at ambient temperature. Cholera culture was performed from wet filter paper inoculated with stool. Molecular detection of Vibrio cholerae O1 by PCR was done from dry Whatman 903 filter papers inoculated with stool, and from wet filter paper supernatant. In August and September 2015, 101 consecutive suspected cholera cases were enrolled, of which 36 were confirmed by PCR. The enriched RDT had 86.1% (95% CI: 70.5-95.3) sensitivity and 100% (95% CI: 94.4-100) specificity compared to PCR as the reference standard. The sensitivity of culture versus PCR was 83.3% (95% CI: 67.2-93.6) for culture performed on site and 72.2% (95% CI: 54.8-85.8) at the international reference laboratory, where samples were tested after an average delay of two months after sample collection, and specificity was 98.5% (95% CI: 91.7-100) and 100% (95% CI: 94.5-100), respectively. The RDT with enrichment showed performance comparable to that of culture and could be a sustainable alternative to culture confirmation where laboratory capacity is limited

Results of the enriched RDT and of culture at National Public Health Laboratory, Juba, and at Institut Pasteur, Paris, compared to PCR results.

<p>Results of the enriched RDT and of culture at National Public Health Laboratory, Juba, and at Institut Pasteur, Paris, compared to PCR results.</p

Diagnostic performance of direct and enriched RDT, and of culture at National Public Health Laboratory, Juba, and at Institut Pasteur, Paris, using PCR as the reference standard in all (N = 101) or patients without prior antibiotics (N = 80).

<p>Diagnostic performance of direct and enriched RDT, and of culture at National Public Health Laboratory, Juba, and at Institut Pasteur, Paris, using PCR as the reference standard in all (N = 101) or patients without prior antibiotics (N = 80).</p

Effectiveness of one dose of oral cholera vaccine in response to an outbreak: a case-cohort study

Background: Oral cholera vaccines represent a new effective tool to fight cholera and are licensed as two-dose regimens with 2–4 weeks between doses. Evidence from previous studies suggests that a single dose of oral cholera vaccine might provide substantial direct protection against cholera. During a cholera outbreak in May, 2015, in Juba, South Sudan, the Ministry of Health, Médecins Sans Frontières, and partners engaged in the first field deployment of a single dose of oral cholera vaccine to enhance the outbreak response. We did a vaccine effectiveness study in conjunction with this large public health intervention. Methods: We did a case-cohort study, combining information on the vaccination status and disease outcomes from a random cohort recruited from throughout the city of Juba with that from all the cases detected. Eligible cases were those aged 1 year or older on the first day of the vaccination campaign who sought care for diarrhoea at all three cholera treatment centres and seven rehydration posts throughout Juba. Confirmed cases were suspected cases who tested positive to PCR for Vibrio cholerae O1. We estimated the short-term protection (direct and indirect) conferred by one dose of cholera vaccine (Shanchol, Shantha Biotechnics, Hyderabad, India). Findings: Between Aug 9, 2015, and Sept 29, 2015, we enrolled 87 individuals with suspected cholera, and an 898-person cohort from throughout Juba. Of the 87 individuals with suspected cholera, 34 were classified as cholera positive, 52 as cholera negative, and one had indeterminate results. Of the 858 cohort members who completed a follow-up visit, none developed clinical cholera during follow-up. The unadjusted single-dose vaccine effectiveness was 80·2% (95% CI 61·5–100·0) and after adjusting for potential confounders was 87·3% (70·2–100·0). Interpretation: One dose of Shanchol was effective in preventing medically attended cholera in this study. These results support the use of a single-dose strategy in outbreaks in similar epidemiological settings. Funding: Médecins Sans Frontières