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. 2011 Jan 25;5(1):e1006.
doi: 10.1371/journal.pntd.0001006.

Use of oral cholera vaccines in an outbreak in Vietnam: a case control study

Dang Duc Anh  1 , Anna Lena Lopez, Vu Dinh Thiem, Shannon L Grahek, Tran Nhu Duong, Jin Kyung Park, Hye Jung Kwon, Michael Favorov, Nguyen Tran Hien, John D Clemens
Affiliations

Use of oral cholera vaccines in an outbreak in Vietnam: a case control study

Dang Duc Anh et al. PLoS Negl Trop Dis. .

Abstract

Background: Killed oral cholera vaccines (OCVs) are available but not used routinely for cholera control except in Vietnam, which produces its own vaccine. In 2007-2008, unprecedented cholera outbreaks occurred in the capital, Hanoi, prompting immunization in two districts. In an outbreak investigation, we assessed the effectiveness of killed OCV use after a cholera outbreak began.

Methodology/principal findings: From 16 to 28 January 2008, vaccination campaigns with the Vietnamese killed OCV were held in two districts of Hanoi. No cholera cases were detected from 5 February to 4 March 2008, after which cases were again identified. Beginning 8 April 2008, residents of four districts of Hanoi admitted to one of five hospitals for acute diarrhea with onset after 5 March 2008 were recruited for a matched, hospital-based, case-control outbreak investigation. Cases were matched by hospital, admission date, district, gender, and age to controls admitted for non-diarrheal conditions. Subjects from the two vaccinated districts were evaluated to determine vaccine effectiveness. 54 case-control pairs from the vaccinated districts were included in the analysis. There were 8 (15%) and 16 (30%) vaccine recipients among cases and controls, respectively. The vaccine was 76% protective against cholera in this setting (95% CI 5% to 94%, P = 0.042) after adjusting for intake of dog meat or raw vegetables and not drinking boiled or bottled water most of the time.

Conclusions/significance: This is the first study to explore the effectiveness of the reactive use of killed OCVs during a cholera outbreak. Our findings suggest that killed OCVs may have a role in controlling cholera outbreaks.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Map of Vietnam indicating cholera endemic areas in the Central coastal regions and in the South where cholera vaccines were used from 1997 to 2005.
Figure 2
Figure 2. Clinical cholera cases in Hanoi, 2007 to 2008.
Figure 3
Figure 3. Urban districts of Hanoi showing Hoang Mai and Thanh Xuan, where mass vaccination campaigns were held in January 2008, and Dong Da and Cau Giay, the unvaccinated districts included in the study.
Figure 4
Figure 4. Flowchart of cases and controls in the study.
See this image and copyright information in PMC

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