Effectiveness of reactive oral cholera vaccination in rural Haiti: a case-control study and bias-indicator analysis

Ivers, Louise C.; Hilaire, Isabelle J.; Teng, Jessica E.; Almazor, Charles Patrick; Jerome, J. Gregory; Ternier, Ralph; Boncy, Jacques; Buteau, Josiane; Murray, Megan; Harris, Jason B.; Franke, Molly F.

doi:10.1016/s2214-109x(14)70368-7

Cited by 87 publications

(90 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 Our colleagues in the Artibonite valley have recently reported an estimated VE of 65% at their site using a casecontrol design. 26 Our study reports that only 18 cases of cholera occurred in the patients who had received at least one dose. Although a small group, this argues for effectiveness of even a single dose of vaccine.…”

Section: Discussionmentioning

confidence: 76%

Effectiveness of Oral Cholera Vaccine in Haiti: 37-Month Follow-Up

Sévère¹,

Rouzier²,

Anglade³

et al. 2016

The American Society of Tropical Medicine and Hygiene

View full text Add to dashboard Cite

Abstract. The first oral cholera vaccine (OCV) campaign, since its prequalification by the World Health Organization, in response to an ongoing cholera epidemic (reactive vaccination) was successfully conducted in a poor urban slum of approximately 70,000 inhabitants in Port-au-Prince, Haiti, in 2012. Vaccine coverage was 75% of the target population. This report documents the impact of OCV in reducing the number of culture-confirmed cases of cholera admitted to the Groupe Haïtien d'Etude du Sarcome de Kaposi et des Infections Opportunistes (GHESKIO) cholera treatment center from that community in the 37 months postvaccination (April 2012-April 30, 2015. Of 1,788 patients with cultureconfirmed cholera, 1,770 (99%) were either from outside the vaccine area (1,400 cases) or from the vaccinated community who had not received OCV (370 cases). Of the 388 people from the catchment area who developed culture-confirmed cholera, 370 occurred among the 17,643 people who had not been vaccinated (2.1%) and the remaining 18 occurred among the 52,357 people (0.034%) who had been vaccinated (P < 0.001), for an efficacy that approximates 97.5%. Despite not being designed as a randomized control trial, the very high efficacy is a strong evidence for the effectiveness of OCV as part of an integrated package for the control of cholera in outbreak settings.

show abstract

Section: Discussionmentioning

confidence: 76%

Effectiveness of Oral Cholera Vaccine in Haiti: 37-Month Follow-Up

Sévère¹,

Rouzier²,

Anglade³

et al. 2016

The American Society of Tropical Medicine and Hygiene

View full text Add to dashboard Cite

show abstract

“…In another example, several VE case-control studies for cholera vaccines have used confirmed cholera diarrhea as cases and chose as controls persons who did not seek treatment for diarrhea -a conventional design (65)(66)(67). They then did a parallel "bias-indicator" analysis using those who sought treatment for diarrhea but did not test positive for cholera as cases and conventional controls, showing that the study design did not find measurable VE for a noncholera outcome.…”

Section: Discussionmentioning

confidence: 99%

“…• Showed that the vaccine-preventable burden of influenza mortality has been overestimated due to confounding (6,14,15) • Added confidence to several studies of cholera VE in outbreaks by showing that VE was estimated to be not statistically different from zero for non-cholera diarrhea (65)(66)(67) Substantive insights from test-negative designs…”

Section: Discussionmentioning

confidence: 99%

Observational studies and the difficult quest for causality: lessons from vaccine effectiveness and impact studies

2016

View full text Add to dashboard Cite

Although randomized placebo-controlled trials (RCT) are critical to establish efficacy of vaccines at the time of licensure, important remaining questions about vaccine effectiveness (VE) -used here to include individual-level measures and population-wide impact of vaccine programs --can only be answered once the vaccine is in use, from observational studies. However, such studies are inherently at risk for bias. Using a causal framework and illustrating with examples we review newer approaches to detecting and avoiding confounding and selection bias in three major classes of observational study design: cohort, case-control, and ecological studies. Studies of influenza VE, especially in seniors, are an excellent demonstration of the challenges of detecting and reducing such bias, and so we use influenza VE as a running example. We take a fresh look at the time-trend studies often dismissed as "ecological." Such designs are the only observational study design that can measure the overall effect of a vaccination program (indirect (herd) as well as direct effects), and are in fact already an important part of the evidence base for several vaccines currently in use. Despite the great strides towards more robust observational study designs, challenges lie ahead for evaluating best practices for achieving robust unbiased results from observational studies. This is critical for evaluation of national and global vaccine program effectiveness.

show abstract

“…(17) Early OCV effectiveness estimates from this campaign suggested effectiveness of 58 to 63%. (6) Further OCV campaigns using the same vaccine occurred in subsequent years targeting an additional 395,000 people in high cholera-incidence communities.…”

Section: Methodsmentioning

confidence: 99%

Comparison of two control groups for estimation of oral cholera vaccine effectiveness using a case-control study design

Franke

Jerome²,

Matias

et al. 2017

Vaccine

Self Cite

View full text Add to dashboard Cite

Background Case-control studies to quantify oral cholera vaccine effectiveness (VE) often rely on neighbors without diarrhea as community controls. Test-negative controls can be easily recruited and may minimize bias due to differential health-seeking behavior and recall. We compared VE estimates derived from community and test-negative controls and conducted bias-indicator analyses to assess potential bias with community controls. Methods From October 2012 through November 2016, patients with acute watery diarrhea were recruited from cholera treatment centers in rural Haiti. Cholera cases had a positive stool culture. Non-cholera diarrhea cases (test-negative controls and non-cholera diarrhea cases for bias-indicator analyses) had a negative culture and rapid test. Up to four community controls were matched to diarrhea cases by age group, time, and neighborhood. Results Primary analyses included 181 cholera cases, 157 non-cholera diarrhea cases, 716 VE community controls and 625 bias-indicator community controls. VE for self-reported vaccination with two doses was consistent across the two control groups, with statistically significant VE estimates ranging from 72 to 74%. Sensitivity analyses revealed similar, though somewhat attenuated estimates for self-reported two dose VE. Bias-indicator estimates were consistently less than one, with VE estimates ranging from 19 to 43%, some of which were statistically significant. Conclusions OCV estimates from case-control analyses using community and test-negative controls were similar. While bias-indicator analyses suggested possible over-estimation of VE estimates using community controls, test-negative analyses suggested this bias, if present, was minimal. Test-negative controls can be a valid low-cost and time-efficient alternative to community controls for OCV effectiveness estimation and may be especially relevant in emergency situations.

show abstract

Effectiveness of reactive oral cholera vaccination in rural Haiti: a case-control study and bias-indicator analysis

Cited by 87 publications

References 25 publications

Effectiveness of Oral Cholera Vaccine in Haiti: 37-Month Follow-Up

Effectiveness of Oral Cholera Vaccine in Haiti: 37-Month Follow-Up

Observational studies and the difficult quest for causality: lessons from vaccine effectiveness and impact studies

Comparison of two control groups for estimation of oral cholera vaccine effectiveness using a case-control study design

Contact Info

Product

Resources

About