title: Analysis of vaccination campaign effectiveness and population immunity to support and sustain polio elimination in Nigeria.
abstract: BACKGROUND
  The world is closer than ever to a polio-free Africa. In this end-stage, it is important to ensure high levels of population immunity to prevent polio outbreaks. Here, we introduce a new method of assessing vaccination campaign effectiveness and estimating immunity at the district-level. We demonstrate how this approach can be used to plan the vaccination campaigns prospectively to better manage population immunity in Northern Nigeria.
  
  
  METHODS
  Using Nigerian acute flaccid paralysis surveillance data from 2004-2014, we developed a Bayesian hierarchical model of campaign effectiveness and compared it to lot-quality assurance sampling data. We then used reconstructed sero-specific population immunity based on campaign history and compared district estimates of immunity to the occurrence of confirmed poliovirus cases.
  
  
  RESULTS
  Estimated campaign effectiveness has improved across northern Nigeria since 2004, with Kano state experiencing an increase of 40 % (95 % CI, 26-54 %) in effectiveness from 2013 to 2014. Immunity to type 1 poliovirus has increased steadily. On the other hand, type 2 immunity was low and variable until the recent use of trivalent oral polio vaccine. We find that immunity estimates are related to the occurrence of both wild and vaccine-derived poliovirus cases and that campaign effectiveness correlates with direct measurements using lot-quality assurance sampling. Future campaign schedules highlight the trade-offs involved with using different vaccine types.
  
  
  CONCLUSIONS
  The model in this study provides a novel method for assessing vaccination campaign performance and epidemiologically-relevant estimates of population immunity. Small-area estimates of campaign effectiveness can then be used to evaluate prospective campaign plans. This modeling approach could be applied to other countries as well as other vaccine preventable diseases.
authors.affiliation: Institute for Disease Modeling, Bellevue, WA, USA.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Upfill-Brown
authors.affiliation: Bill & Melinda Gates Foundation, Seattle, WA, USA.
authors.forename: Arend
authors.initials: A
authors.lastname: Voorman
authors.affiliation: Institute for Disease Modeling, Bellevue, WA, USA.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Chabot-Couture
authors.affiliation: Federal Ministry of Health, Federal Republic of Nigeria, Abuja, FCT, Nigeria.|National Polio Emergency Operations Center, Abuja, FCT, Nigeria.
authors.forename: Faisal
authors.initials: F
authors.lastname: Shuaib
authors.affiliation: Institute for Disease Modeling, Bellevue, WA, USA. hlyons@intven.com.
authors.forename: Hil M
authors.identifier: http://orcid.org/0000-0002-0325-006X
authors.initials: HM
authors.lastname: Lyons
mesh_terms: D000349:Africa; D001499:Bayes Theorem; D006801:Humans; D009549:Nigeria / Q000453:epidemiology; D011051:Poliomyelitis / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control*; D011055:Poliovirus Vaccine, Oral; D011446:Prospective Studies; D014611:Vaccination
chemical_list: D011055:Poliovirus Vaccine, Oral
keywords: Campaigns; Coverage; Eradication; Hierarchical modeling; Immunity; Nigeria; Polio; Supplementary immunization activities