title: Seroprevalence and Determinants of Immunity to Diphtheria for Children Living in Two Districts of Contrasting Incidence During an Outbreak in East Java, Indonesia.
abstract: BACKGROUND
  In 2012, an ongoing outbreak of diphtheria in Indonesia was focused in the province of East Java. There was a need to assess vaccine coverage and immunity gaps in children.
  
  
  METHODS
  We conducted a cross-sectional seroprevalence and vaccine coverage survey of children 1-15 years of age in 2 districts of East Java: one of high incidence (on the island of Madura) and one of low incidence (on the mainland). From each district, we sampled 150 children (10 children per year of age). Sera and throat swabs were taken to determine immunity and carriage status. Immunity was defined as ≥0.1 international unit/mL of antibody to diphtheria toxin.
  
  
  RESULTS
  A total of 297 children were selected to participate in the study. Coverage of three doses of combined vaccine for diphtheria, tetanus and pertussis was significantly lower (P < 0.001) in the high incidence district compared with the low [57%, 95% confidence interval (CI): 36-78 vs. 97%, 95% CI: 93-100]. Despite this higher vaccine coverage, seroprevalence of immunity was lower in the low incidence district compared with the high (71%, 95% CI: 63-80 vs. 83%, 95% CI: 76-90). Immunity in the high incidence district was associated with increased age, increased prevalence of toxigenic Corynebacterium diphtheriae carriers and with receipt of multiple (and likely more recent) boosters.
  
  
  CONCLUSIONS
  Significant variation exists in vaccine coverage and seroprevalence of immunity to diphtheria in East Java. Immunity in high incidence districts is likely because of natural immunity acquired through exposure to toxigenic C. diphtheriae. Booster vaccines are essential for achieving protective levels of immunity.
authors.affiliation: From the *Field Epidemiology Training Programme, Public Health England, London, United Kingdom; †Academic Unit of Public Health, Leeds Institute of Health Sciences, University of Leeds, Leeds, United Kingdom; ‡European Programme for Public Health Microbiology Training, European Centres for Disease Prevention and Control, Stockholm, Sweden; §World Health Organisation Collaborating Centre for Reference and Research on Diphtheria and Streptococcal Infections, Public Health England, London, United Kingdom; ¶Airlangga University, Surabaya, Indonesia; ‖Balai Besar Laboratorium Kesehatan, Surabaya, Indonesia; and **Public Health England, London, United Kingdom.
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Hughes
authors.forename: Amy F W
authors.initials: AF
authors.lastname: Mikhail
authors.forename: Dominicus
authors.initials: D
authors.lastname: Husada
authors.forename: Eveline
authors.initials: E
authors.lastname: Irawan
authors.forename: George
authors.initials: G
authors.lastname: Kafatos
authors.forename: Samantha
authors.initials: S
authors.lastname: Bracebridge
authors.forename: Richard
authors.initials: R
authors.lastname: Pebody
authors.forename: Androulla
authors.initials: A
authors.lastname: Efstratiou
mesh_terms: D000293:Adolescent; D002353:Carrier State / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004165:Diphtheria / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000276:immunology; D005260:Female; D006801:Humans; D015994:Incidence; D007214:Indonesia / Q000453:epidemiology; D007223:Infant; D008297:Male; D010614:Pharynx / Q000382:microbiology; D016036:Seroepidemiologic Studies; D014611:Vaccination / Q000706:statistics & numerical data
chemical_list: D015721:Diphtheria-Tetanus-Pertussis Vaccine