title: A Preliminary Assessment of Rotavirus Vaccine Effectiveness in Zambia.
abstract: BACKGROUND
  Diarrhea is the third leading cause of child death in Zambia. Up to one-third of diarrhea cases resulting in hospitalization and/or death are caused by vaccine-preventable rotavirus. In January 2012, Zambia initiated a pilot introduction of the Rotarix live, oral rotavirus vaccine in all public health facilities in Lusaka Province.
  
  
  METHODS
  Between July 2012 and October 2013, we conducted a case-control study at 6 public sector sites to estimate rotavirus vaccine effectiveness (VE) in age-eligible children presenting with diarrhea. We computed the odds of having received at least 1 dose of Rotarix among children whose stool was positive for rotavirus antigen (cases) and children whose stool was negative (controls). We adjusted the resulting odds ratio (OR) for patient age, calendar month of presentation, and clinical site, and expressed VE as (1 - adjusted OR) × 100.
  
  
  RESULTS
  A total of 91 rotavirus-positive cases and 298 rotavirus-negative controls who had under-5 card-confirmed vaccination status and were ≥6 months of age were included in the case-control analysis. Among rotavirus-positive children who were age-eligible to be vaccinated, 20% were hospitalized. Against rotavirus diarrhea of all severity, the adjusted 2-dose VE was 26% (95% confidence interval [CI], -30% to 58%) among children ≥6 months of age. VE against hospitalized children ≥6 months of age was 56% (95% CI, -34% to 86%).
  
  
  CONCLUSIONS
  We observed a higher point estimate for VE against increased severity of illness compared with milder disease, but were not powered to detect a low level of VE against milder disease.
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Laura K
authors.initials: LK
authors.lastname: Beres
authors.affiliation: Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jacqueline E
authors.initials: JE
authors.lastname: Tate
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka.
authors.forename: Lungowe
authors.initials: L
authors.lastname: Njobvu
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka.
authors.forename: Bertha
authors.initials: B
authors.lastname: Chibwe
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Rudd
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka.
authors.forename: M Brad
authors.initials: MB
authors.lastname: Guffey
authors.affiliation: University of North Carolina School of Medicine, Chapel Hill.
authors.forename: Jeffrey S A
authors.initials: JS
authors.lastname: Stringer
authors.affiliation: Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Umesh D
authors.initials: UD
authors.lastname: Parashar
authors.affiliation: Centre for Infectious Disease Research in Zambia, Lusaka.
authors.forename: Roma
authors.initials: R
authors.lastname: Chilengi
mesh_terms: D000956:Antigens, Viral / Q000276:immunology; D016022:Case-Control Studies; D002675:Child, Preschool; D003967:Diarrhea / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D005243:Feces / Q000821:virology; D005260:Female; D006760:Hospitalization; D006801:Humans; D000071497:Immunogenicity, Vaccine; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016017:Odds Ratio; D012401:Rotavirus / Q000276:immunology; D012400:Rotavirus Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D022243:Rotavirus Vaccines / Q000008:administration & dosage / Q000276:immunology*; D012720:Severity of Illness Index; D014611:Vaccination / Q000706:statistics & numerical data; D064166:Vaccine Potency; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D015024:Zambia / Q000453:epidemiology
chemical_list: D000956:Antigens, Viral; C492457:RIX4414 vaccine; D022243:Rotavirus Vaccines; D014613:Vaccines, Attenuated
keywords: Zambia; immunization; rotavirus; rotavirus vaccine; vaccine effectiveness