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

• Published in: PLoS Neglected Tropical Diseases
• Main Authors: Dang Duc Anh, 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
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2011
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270; Arctic
• Online Access: https://doi.org/10.1371/journal.pntd.0001006; https://doaj.org/article/cea54587506c4f178fb68de91a1b137d

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.