Effectiveness of a Bivalent Killed Whole Cell Based Oral Cholera Vaccine

Study Overview
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Brief Summary
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Various field studies has found that the modified , bivalent, whole cell - based oral cholera vaccine (OCV) to be safe, immunogenic and effective with protective efficacy of 67 % in earlier clinical trials. However, the effectiveness of the vaccine in real life situation using the public health system is unknown. It is critical to follow up in the same population, where pilot introduction of OCV was introduced and evaluate vaccine proactive effectiveness at individual as well as at population level. The follow - up and determination of effectiveness of mass OCV vaccination was requested by State Government.

Detailed Description
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The overall goal of this study is to evaluate the protective effectiveness of one or two doses of modified, bivalent, killed whole cell based OCV, given at least 14 days apart, when delivered through community - based mass vaccination campaign using existing public health infrastructure in a high - risk population in Satyabadi block of Puri district, Orissa, India. This study has following objectives Primary objectives: * To evaluate the individual level protective effectiveness of one or two doses of OCV against culture confirmed cholera episodes, severe enough to seek a formal health care. Secondary objectives: To evaluate population - level effectiveness (herd effects)of OCV delivered through a community based mass vaccination when the vaccine is delivered to more than half of population at risk. To determine inverse correlation between vaccine coverage and cholera incidence among diverse geographical clusters.

Official Title
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Effectiveness of a Bivalent, Killed Whole-cell Based Oral Cholera Vaccine(Shanchol®) Delivered Through Community-based Mass Vaccination Campaign in a High-risk Population in India: Matched Case-control Studies

Conditions
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Cholera

Participation Criteria
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Eligibility Criteria
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Inclusion criteria for cases of the main case-control study are as follows: Giving verbal informed consent/assent, or in the case of minors, a parent or guardian give informed consent to participate in the study Living in the study area since the start of the mass vaccination Submitted a faecal specimen Whose residence could be located Whose stool specimens yield V. cholera O1 or O139 Belonging to study population through census database Exclusion criteria: Not giving verbal informed consent/assent, or in the case of minors, a parent or guardian does not give informed consent to participate in the study Not living in the study area since the start of the mass vaccination No faecal specimen Whose residence could not be located Whose stool specimens does not yield V. cholera O1 or O139 Not belonging to study population through census database

Ages Eligible for Study
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Minimum Age: 1 Year

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Cholera cases group<br>Any diarrheal cases or suspected cholera cases from study area, whose stool specimen collected in study health center and examined in reference laboratory, reveals V. cholerae serotype O1/O139 is defined as cholera case | |
| Control group<br>A randomly selected age matched individual, who have been living in the study area and did not seek care for diarrheal illness in the study health center since vaccination is defined as control | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Vaccine protective effectiveness at individual level | Matched controls will be selected among the persons of the same age group as that of each case. 1 to 4 ratio will be used in matching cases to controls.Information on all other exposure variables will be collected through questionaire interview for both cases and controls.Protective effectiveness (PE) (%) = [1- the odds of vaccination among cholera confirmed cases relative to the odds of vaccination among matched controls] × 100 is the metric to measure vaccine protective effectiveness at individual level. | 11 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Population level effectiveness (herd effect) | Indirect effect: Fraction of household members who are vaccinated in households of unvaccinated cases compared with fraction of household members who are vaccinated in households of unvaccinated controls Total effect: Fraction of household members who are vaccinated in households of vaccinated cases compared with the fraction of household members who are vaccinated in households of vaccinated controls. Overall effects: Fraction of household members who are vaccinated in household of cases compared with fraction of household members who are vaccinated in control households. | 11 months | 
| Cohort / GIS study for the measure of herd protection | Geographic unit as a cluster for evaluating vaccine herd protection with the use of cohort analysis, using GIS information from the baseline census. Here, there will be comparison in the incidence of the target outcome (cholera or non-cholera diarrhea) according to the level of vaccine coverage of the geographic unit. | 11 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Oral, Cholera, Vaccine, Herd, Risk, population, Matched, Control, Case, Bias