title: Measles vaccine effectiveness in standard and early immunization strategies, Niger, 1995.
abstract: BACKGROUND
  An Expanded Programme on Immunization was started in late 1987 in Niger, including vaccination against measles with one dose of standard titer Schwarz vaccine given to infants after 9 months of age. During epidemics an early two-dose strategy was implemented (one dose between 6 and 8 months and one dose after 9 months). From January 1, 1995, until May 7, 1995, 13 892 measles cases were reported in Niamey, Niger.
  
  
  METHODS
  A retrospective cohort study was conducted in a crowded area of Niamey at the end of the outbreak to assess the effectiveness of measles vaccine in standard (after 9 months) and early (before 9 months) immunization strategies under field conditions.
  
  
  RESULTS
  Highest measles incidence rates were observed among children <1 year of age. Vaccine effectiveness estimates increased with age at vaccination from 78% with a single dose administered at 6 months of age to 95% at 9 months. Vaccine effectiveness with the early two dose strategy was 93%.
  
  
  CONCLUSIONS
  Immunization with a single dose of standard titer Schwarz vaccine before 9 months of age provided higher clinical protection than expected from seropositivity studies. The early two dose strategy is justified in contexts where measles incidence is high before 9 months of age. Our results raise the issue of lowering the recommended age for measles vaccination in developing countries.
authors.affiliation: Epicentre, Paris, France. epimail@epicentre.msf.org
authors.forename: A V
authors.initials: AV
authors.lastname: Kaninda
authors.forename: D
authors.initials: D
authors.lastname: Legros
authors.forename: I M
authors.initials: IM
authors.lastname: Jataou
authors.forename: P
authors.initials: P
authors.lastname: Malfait
authors.forename: M
authors.initials: M
authors.lastname: Maisonneuve
authors.forename: C
authors.initials: C
authors.lastname: Paquet
authors.forename: A
authors.initials: A
authors.lastname: Moren
mesh_terms: D002675:Child, Preschool; D003906:Developing Countries; D004196:Disease Outbreaks / Q000517:prevention & control; D006801:Humans; D017589:Immunization Programs; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control; D008458:Measles Vaccine / Q000008:administration & dosage*; D009548:Niger / Q000453:epidemiology; D012189:Retrospective Studies
chemical_list: D008458:Measles Vaccine