title: Use of oral cholera vaccines in an outbreak in Vietnam: a case control study.
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.
  
  
  RESULTS
  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
  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.
authors.affiliation: National Institute of Hygiene and Epidemiology (NIHE), Hanoi, Vietnam.
authors.forename: Dang Duc
authors.initials: DD
authors.lastname: Anh
authors.forename: Anna Lena
authors.initials: AL
authors.lastname: Lopez
authors.forename: Vu Dinh
authors.initials: VD
authors.lastname: Thiem
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Grahek
authors.forename: Tran Nhu
authors.initials: TN
authors.lastname: Duong
authors.forename: Jin Kyung
authors.initials: JK
authors.lastname: Park
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Kwon
authors.forename: Michael
authors.initials: M
authors.lastname: Favorov
authors.forename: Nguyen Tran
authors.initials: NT
authors.lastname: Hien
authors.forename: John D
authors.initials: JD
authors.lastname: Clemens
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002771:Cholera / Q000453:epidemiology* / Q000517:prevention & control*; D022121:Cholera Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D014744:Vietnam / Q000453:epidemiology; D055815:Young Adult
chemical_list: D022121:Cholera Vaccines; D015164:Vaccines, Inactivated