title: Infant vaccination timing: Beyond traditional coverage metrics for maximizing impact of vaccine programs, an example from southern Nepal.
abstract: BACKGROUND
  Immunization programs currently measure coverage by assessing the proportion of children 12-24 months who have been immunized but this does not address the important question of when the scheduled vaccines were administered. Data capturing the timing of vaccination in first 6 months, when severe disease is most likely to occur, are limited.
  
  
  OBJECTIVE
  To estimate the time to Bacillus Calmette-Guérin (BCG) (recommended at birth), diphtheria-tetanus-pertussis-H, influenza b-hepatitis B (DTP-Hib-HepB), and oral polio vaccine (OPV) (recommended at 6, 10, and 14 weeks) vaccinations and risk factors for vaccination delay in infants <6 months of age in a district in southern Nepal where traditional coverage metrics are high.
  
  
  METHODS
  Infants enrolled in a randomized controlled trial of maternal influenza vaccination were visited weekly at home from birth through age 6 months to ascertain if any vaccinations had been given in the prior week. Infant, maternal, and household characteristics were recorded. BCG, DTP-Hib-HepB, and OPV vaccination coverage at 4 and 6 months was estimated. Time to vaccination was estimated through Kaplan-Meier curves; Cox-proportional hazards models were used to examine risk factors for delay for the first vaccine.
  
  
  RESULTS
  The median age of BCG, first OPV and DTP-Hib-HepB receipt was 22, 21, and 18 weeks, respectively. Almost half of infants received no BCG by age 6 months. Only 8% and 7% of infants had received three doses of OPV and DTP-Hib-HepB, respectively, by age 6 months.
  
  
  CONCLUSIONS
  A significant delay in receipt of infant vaccines was found in a prospective, population-based, cohort in southern Nepal despite traditional coverage metrics being high. Immunization programs should consider measuring time to receipt relative to the official schedule in order to maximize benefits for disease control and child health.
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Department of International Health, Global Disease Epidemiology and Control, 615 North Wolfe Street, Baltimore, MD 21205, USA. Electronic address: michelle.hughes@jhu.edu.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Hughes
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Department of International Health, Global Disease Epidemiology and Control, 615 North Wolfe Street, Baltimore, MD 21205, USA. Electronic address: jkatz@jhu.edu.
authors.forename: Joanne
authors.initials: J
authors.lastname: Katz
authors.affiliation: University of Washington, Seattle Children's Hospital, 4800 Sand Point Way NE, MA 7.234, Seattle, WA 98105, USA. Electronic address: Janet.englund@seattlechildrens.org.
authors.forename: Janet A
authors.initials: JA
authors.lastname: Englund
authors.affiliation: Nepal Nutrition Intervention Project - Sarlahi, Kathmandu, Nepal. Electronic address: skhatry@wlink.com.np.
authors.forename: Subarna K
authors.initials: SK
authors.lastname: Khatry
authors.affiliation: Tribhuvan University Teaching Hospital, Department of Paediatrics, Institute of Medicine, Maharajgunj, Kathmandu, Nepal. Electronic address: laxmanshree@yahoo.com.
authors.forename: Laxman
authors.initials: L
authors.lastname: Shrestha
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Department of International Health, Global Disease Epidemiology and Control, 615 North Wolfe Street, Baltimore, MD 21205, USA; Nepal Nutrition Intervention Project - Sarlahi, Kathmandu, Nepal. Electronic address: steveleclerq@gmail.com.
authors.forename: Steven C
authors.initials: SC
authors.lastname: LeClerq
authors.affiliation: Cincinnati Children's Hospital and Medical Center, Global Health Center, R8508, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. Electronic address: mark.steinhoff@cchmc.org.
authors.forename: Mark
authors.initials: M
authors.lastname: Steinhoff
authors.affiliation: George Washington University Milken Institute School of Public Health, Department of Global Health, 950 New Hampshire Avenue, Washington, DC 20052, USA. Electronic address: jtielsch@gwu.edu.
authors.forename: James M
authors.initials: JM
authors.lastname: Tielsch
mesh_terms: D001500:BCG Vaccine / Q000008:administration & dosage*; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000008:administration & dosage*; D005260:Female; D018073:Haemophilus Vaccines / Q000008:administration & dosage*; D017325:Hepatitis B Vaccines / Q000008:administration & dosage*; D006801:Humans; D017589:Immunization Programs; D007115:Immunization Schedule; D007223:Infant; D007231:Infant, Newborn; D053208:Kaplan-Meier Estimate; D008297:Male; D009390:Nepal; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D001500:BCG Vaccine; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D018073:Haemophilus Vaccines; D017325:Hepatitis B Vaccines; D011055:Poliovirus Vaccine, Oral; C122182:diphtheria-tetanus-acellular pertussis-Hib-hepatitis B vaccine
keywords: Childhood immunization; Nepal; Vaccination coverage; Vaccination timeliness