title: Diphtheria outbreak in Lao People's Democratic Republic, 2012-2013.
abstract: Diphtheria is a vaccine-preventable disease. When vaccination coverage and population immunity are low, outbreaks can occur. We investigated a diphtheria outbreak in Lao People's Democratic Republic that occurred during 2012-2013 and highlighted challenges in immunization services delivery to children in the country.
  
  
  
  We reviewed diphtheria surveillance data from April 1, 2012-May 31, 2013. A diphtheria case was defined as a respiratory illness consisting of pharyngitis, tonsillitis, or laryngitis, and an adherent tonsillar or nasopharyngeal pseudomembrane. To identify potential risk factors for diphtheria, we conducted a retrospective case-control study with two aged-matched neighborhood controls per case-patient in Houaphan Province, using bivariate analysis to calculate matched odds ratio (mOR) with 95% confidence intervals (CI). Reasons for non-vaccination among unvaccinated persons were assessed.
  
  
  
  Sixty-two clinical cases of diphtheria and 12 diphtheria-related deaths were reported in seven of 17 provinces. Among case-patients, 43 (69%) were <15years old, five (8%) reported receiving three DTP doses (DTP3), 21 (34%) had received no DTP doses, and 35 (56%) had unknown vaccination status. For the case-control study, 42 of 52 diphtheria case-patients from Houaphan province and 79 matched-controls were enrolled. Five (12%) case-patients and 20 (25%) controls had received DTP3 (mOR=0.4, CI=0.1-1.7). No diphtheria toxoid-containing vaccine was received by 20 (48%) case-patients and 38 (46%) controls. Among case-patients and controls with no DTP dose, 43% of case-patients and 40% of controls lacked access to routine immunization services.
  
  
  
  Suboptimal DTP3 coverage likely caused the outbreak. To prevent continued outbreaks, access to routine immunization services should be strengthened, outreach visits need to be increased, and missed opportunities need to be minimized. In the short term, to rapidly increase population immunity, three rounds of DTP immunization campaign should be completed, targeting children aged 0-14years in affected provinces.
authors.affiliation: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, United States. Electronic address: seinc@who.int.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Sein
authors.affiliation: Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, United States.
authors.forename: Tejpratap
authors.initials: T
authors.lastname: Tiwari
authors.affiliation: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, United States.
authors.forename: Adam
authors.initials: A
authors.lastname: Macneil
authors.affiliation: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, United States.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Wannemuehler
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Lao People's Democratic Republic.
authors.forename: Chanthavy
authors.initials: C
authors.lastname: Soulaphy
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Lao People's Democratic Republic.
authors.forename: Phouthone
authors.initials: P
authors.lastname: Souliphone
authors.affiliation: World Health Organization, Lao People's Democratic Republic.
authors.forename: Rita
authors.initials: R
authors.lastname: Reyburn
authors.affiliation: World Health Organization, Lao People's Democratic Republic.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Ramirez Gonzalez
authors.affiliation: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, United States.
authors.forename: Margaret
authors.initials: M
authors.lastname: Watkins
authors.affiliation: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, United States.
authors.forename: James L
authors.initials: JL
authors.lastname: Goodson
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004165:Diphtheria / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality / Q000517:prevention & control; D004168:Diphtheria Toxoid / Q000008:administration & dosage; D004196:Disease Outbreaks / Q000517:prevention & control; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D007812:Laos / Q000453:epidemiology; D008297:Male; D012189:Retrospective Studies; D014611:Vaccination / Q000379:methods / Q000592:standards*
chemical_list: D004168:Diphtheria Toxoid
keywords: Diphtheria; Lao PDR; Outbreak; Vaccination; Vaccine-preventable