title: Factors influencing completion of multi-dose vaccine schedules in adolescents: a systematic review.
abstract: BACKGROUND
  Completion of multiple dose vaccine schedules is crucial to ensure a protective immune response, and maximise vaccine cost-effectiveness. While barriers and facilitators to vaccine uptake have recently been reviewed, there is no comprehensive review of factors influencing subsequent adherence or completion, which is key to achieving vaccine effectiveness. This study identifies and summarises the literature on factors affecting completion of multi-dose vaccine schedules by adolescents.
  
  
  METHODS
  Ten online databases and four websites were searched (February 2014). Studies with analysis of factors predicting completion of multi-dose vaccines were included. Study participants within 9-19 years of age were included in the review. The defined outcome was completion of the vaccine series within 1 year among those who received the first dose.
  
  
  RESULTS
  Overall, 6159 abstracts were screened, and 502 full texts were reviewed. Sixty one studies were eligible for this review. All except two were set in high-income countries. Included studies evaluated human papillomavirus vaccine, hepatitis A, hepatitis B, and varicella vaccines. Reported vaccine completion rates, among those who initiated vaccination, ranged from 27% to over 90%. Minority racial or ethnic groups and inadequate health insurance coverage were risk factors for low completion, irrespective of initiation rates. Parental healthcare seeking behaviour was positively associated with completion. Vaccine delivery in schools was associated with higher completion than delivery in the community or health facilities. Gender, prior healthcare use and socio-economic status rarely remained significant risks or protective factors in multivariate analysis.
  
  
  CONCLUSIONS
  Almost all studies investigating factors affecting completion have been carried out in developed countries and investigate a limited range of variables. Increased understanding of barriers to completion in adolescents will be invaluable to future new vaccine introductions and the further development of an adolescent health platform. PROSPERO reg# CRD42014006765.
authors.affiliation: Clinical Research Department, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. Katherine.Gallagher@lshtm.ac.uk.|Mwanza Intervention Trials Unit, The National Institute for Medical Research Mwanza Campus, PO Box 11936, Mwanza, Tanzania. Katherine.Gallagher@lshtm.ac.uk.
authors.forename: K E
authors.initials: KE
authors.lastname: Gallagher
authors.affiliation: Department of Epidemiology, University of Washington, 1959 NE Pacific Street, Health Sciences Building F-250, Box 357236, Seattle, WA, 98195-7236, USA. elysekad@gmail.com.
authors.forename: E
authors.initials: E
authors.lastname: Kadokura
authors.affiliation: Departments of Obstetrics and Gynaecology and Global Health, University of Washington, 1959 NE Pacific Street, Health Sciences Building F-250, Box 357236, Seattle, WA, 98195-7236, USA. Eckert@uw.edu.
authors.forename: L O
authors.initials: LO
authors.lastname: Eckert
authors.affiliation: Clinical Research Department, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. sachi.epi@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Miyake
authors.affiliation: Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, 15-17 Tavistock Place, London, WC1H 9SH, UK. Sandra.Mounier-Jack@lshtm.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Mounier-Jack
authors.affiliation: Infections and Cancer Unit, Cancer Epidemiology Research Programme, Catalan Institute of Oncology, Av. Gran Via de l'Hospitalet 199-203, Hospitalet de Llobregat, 08908, Barcelona, Spain. maldea@iconcologia.net.|Bellvitge Institute of Biomedical Research (IDIBELL), Barcelona, Spain. maldea@iconcologia.net.
authors.forename: M
authors.initials: M
authors.lastname: Aldea
authors.affiliation: MRC Tropical Epidemiology Group, Faculty of Epidemiology and Population Health, London school of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. David.Ross@lshtm.ac.uk.
authors.forename: D A
authors.initials: DA
authors.lastname: Ross
authors.affiliation: Clinical Research Department, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. Deborah.Watson-Jones@lshtm.ac.uk.|Mwanza Intervention Trials Unit, The National Institute for Medical Research Mwanza Campus, PO Box 11936, Mwanza, Tanzania. Deborah.Watson-Jones@lshtm.ac.uk.
authors.forename: D
authors.initials: D
authors.lastname: Watson-Jones
mesh_terms: D000293:Adolescent; D019433:Chickenpox Vaccine / Q000008:administration & dosage; D002648:Child; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D022362:Hepatitis A Vaccines / Q000008:administration & dosage; D017325:Hepatitis B Vaccines / Q000008:administration & dosage; D006801:Humans; D007115:Immunization Schedule; D019458:Insurance Coverage / Q000706:statistics & numerical data; D007348:Insurance, Health; D008297:Male; D053918:Papillomavirus Vaccines / Q000008:administration & dosage; D010342:Patient Acceptance of Health Care; D012307:Risk Factors; D014611:Vaccination / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D019433:Chickenpox Vaccine; D022362:Hepatitis A Vaccines; D017325:Hepatitis B Vaccines; D053918:Papillomavirus Vaccines