title: Seroepidemiology of diphtheria and tetanus among children and young adults in Tajikistan: nationwide population-based survey, 2010.
abstract: BACKGROUND
  Tajikistan had a major diphtheria outbreak (≈ 10,000 cases) in the 1990 s, which was controlled after nationwide immunization campaigns with diphtheria-tetanus toxoid in 1995 and 1996. Since 2000, only 52 diphtheria cases have been reported. However, in coverage surveys conducted in 2000 and 2005, diphtheria-tetanus-pertussis vaccine coverage was lower than administratively reported estimates raising concerns about potential immunity gaps. To further assess population immunity to diphtheria in Tajikistan, diphtheria antibody testing was included in a large-scale nationwide serosurvey for vaccine-preventable diseases conducted in connection with a poliomyelitis outbreak in 2010. In addition, the serosurvey provided an opportunity to assess population immunity to tetanus.
  
  
  METHODS
  Residents of all regions of Tajikistan aged 1-24 years were included in the serosurvey implemented during September-October 2010. Participants were selected through stratified cluster sampling. Specimens were tested for diphtheria antibodies using a Vero cell neutralization assay and for tetanus antibodies using an anti-tetanus IgG ELISA. Antibody concentrations ≥ 0.1 IU/mL were considered seropositive.
  
  
  RESULTS
  Overall, 51.4% (95% CI, 47.1%-55.6%) of participants were seropositive for diphtheria and 78.9% (95% CI, 74.7%-82.5%) were seropositive for tetanus. The lowest percentages of seropositivity for both diseases were observed among persons aged 10-19 years: diphtheria seropositivity was 37.1% (95% CI, 31.0%-43.7%) among 10-14 year-olds, and 35.3% (95% CI, 29.9%-41.1%) among 15-19 year-olds; tetanus seropositivity in respective age groups was 65.3% (95% CI, 58.4%-71.6%) and 70.1% (95% CI, 64.5%-75.2%).
  
  
  CONCLUSIONS
  Population immunity for diphtheria in Tajikistan is low, particularly among 10-19 year-olds. Population immunity to tetanus is generally higher than for diphtheria, but is suboptimal among 10-19 year-olds. These findings highlight the need to improve routine immunization service delivery, and support a one-time supplementary immunization campaign with diphtheria-tetanus toxoid among birth cohorts aged 1-19 years in 2010 (3-21 years in 2012) to close immunity gaps and prevent diphtheria outbreaks.
authors.affiliation: Centers for Disease Control and Prevention (CDC), Atlanta, United States. Electronic address: nck7@cdc.gov.
authors.forename: Nino
authors.initials: N
authors.lastname: Khetsuriani
authors.forename: Katherina
authors.initials: K
authors.lastname: Zakikhany
authors.forename: Shamsiddin
authors.initials: S
authors.lastname: Jabirov
authors.forename: Nargis
authors.initials: N
authors.lastname: Saparova
authors.forename: Pavel
authors.initials: P
authors.lastname: Ursu
authors.forename: Kathleen
authors.initials: K
authors.lastname: Wannemuehler
authors.forename: Steve
authors.initials: S
authors.lastname: Wassilak
authors.forename: Androulla
authors.initials: A
authors.lastname: Efstratiou
authors.forename: Rebecca
authors.initials: R
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000907:Antibodies, Bacterial / Q000097:blood*; D000992:Antitoxins / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004165:Diphtheria / Q000453:epidemiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D009500:Neutralization Tests; D016036:Seroepidemiologic Studies; D013620:Tajikistan / Q000453:epidemiology; D013742:Tetanus / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D000992:Antitoxins; D007074:Immunoglobulin G
keywords: Diphtheria; Population immunity; Seroprevalence; Susceptibility; Tajikistan; Tetanus