title: The effect of immunization on measles incidence in the Democratic Republic of Congo: Results from a model of surveillance data.
abstract: BACKGROUND
  Measles continues to be a leading cause of vaccine-preventable disease mortality among children under five despite a safe and efficacious vaccine being readily available. While global vaccination coverage has improved tremendously, measles outbreaks persist throughout sub-Saharan Africa. Since 2010, the Democratic Republic of Congo (DRC) has seen a resurgence of measles outbreaks affecting all 11 provinces. These outbreaks are mainly attributed to gaps in routine immunization (RI) coverage compounded with missed supplementary immunization activities (SIAs). We utilized national passive surveillance data from DRC's Integrated Disease Surveillance and Response (IDSR) system to estimate the effect of immunization on measles incidence in DRC.
  
  
  METHODS
  We investigated the decline in measles incidence post-immunization with one dose of measles containing vaccine (MCV1) with and without the addition of supplementary immunization activities (SIAs) and outbreak response immunization (ORI) campaigns. Measles case counts by health zone were obtained from the IDSR system between January 1, 2010 and December 31, 2013. The impact of measles immunization was modeled using a random effects multi-level model for count data with RI coverage levels and mass campaign activities from one year prior.
  
  
  RESULTS
  The presence of an SIA (aIRR [95% CI] 0.86 [0.60-1.25]) and ORI (0.28 [0.20-0.39]) in the year prior were both associated with a decrease in measles incidence. When interaction terms were included, our results suggested that the high levels of MCV1 reported in the year prior and the presence of either mass campaign was associated with a decrease in measles incidence.
  
  
  CONCLUSIONS
  Our results highlight the importance of a two-dose measles vaccine schedule and the need for a strong routine immunization program coupled with frequent SIAs. Repeated occurrences of large-scale outbreaks in DRC suggest that vaccination coverage rates are grossly overestimated and signify the importance of the evaluation and modification of measles prevention and control strategies.
authors.affiliation: Department of Epidemiology, UCLA Fielding School of Public Health, 650 S Charles E Young Drive, Los Angeles, CA 90095, USA. Electronic address: rhdoshi@ucla.edu.
authors.forename: Reena H
authors.initials: RH
authors.lastname: Doshi
authors.affiliation: Expanded Programme on Immunization, Ave de la Justice, Kinshasa, The Democratic Republic of the Congo. Electronic address: shidicalixte5@yahoo.fr.
authors.forename: Calixte
authors.initials: C
authors.lastname: Shidi
authors.affiliation: Expanded Programme on Immunization, Ave de la Justice, Kinshasa, The Democratic Republic of the Congo. Electronic address: audrymwk@hotmail.fr.
authors.forename: Audry
authors.initials: A
authors.lastname: Mulumba
authors.affiliation: Intellectual Ventures Laboratory, Bellevue, WA, USA. Electronic address: Peckhoff@intven.com.
authors.forename: Philip
authors.initials: P
authors.lastname: Eckhoff
authors.affiliation: Institute of Society and Genetics, UCLA College of Letters & Science, 405 Hilgard Avenue, Los Angeles, CA 90095, USA. Electronic address: cnguyen15@ucla.edu.
authors.forename: Catherine
authors.initials: C
authors.lastname: Nguyen
authors.affiliation: Department of Epidemiology, UCLA Fielding School of Public Health, 650 S Charles E Young Drive, Los Angeles, CA 90095, USA. Electronic address: Nhoff84@ucla.edu.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Hoff
authors.affiliation: Polio Program Bill and Melinda Gates Foundation, 500 Fifth Avenue, North Seattle, WA 98109 USA. Electronic address: Sue.gerber@gatesfoundation.org.
authors.forename: Sue
authors.initials: S
authors.lastname: Gerber
authors.affiliation: Kinshasa School of Public Health, B.P. 127 Kinshasa, Lemba, Kinshasa, The Democratic Republic of the Congo. Electronic address: okitow@yahoo.fr.
authors.forename: Emile
authors.initials: E
authors.lastname: Okitolonda
authors.affiliation: Division of Disease Control, Ministry of Public Health, Ave de la Justice, Kinshasa, The Democratic Republic of the Congo. Electronic address: kebelailunga@gmail.com.
authors.forename: Benoit Kebela
authors.initials: BK
authors.lastname: Ilunga
authors.affiliation: Department of Epidemiology, UCLA Fielding School of Public Health, 650 S Charles E Young Drive, Los Angeles, CA 90095, USA. Electronic address: arimoin@ucla.edu.
authors.forename: Anne W
authors.initials: AW
authors.lastname: Rimoin
mesh_terms: D002675:Child, Preschool; D015023:Democratic Republic of the Congo / Q000453:epidemiology; D004196:Disease Outbreaks; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control*; D008458:Measles Vaccine / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: D008458:Measles Vaccine
keywords: Democratic Republic of Congo; Immunization; Measles; Vaccine-preventable diseases