abstract: 'Extending the benefits of vaccination to everyone who is eligible

  requires an understanding of which populations current vaccination

  efforts have struggled to reach. A clear definition of

  ``hard-to-reach{''''} populations - also known as high-risk or

  marginalized populations, or reaching the last mile - is essential for

  estimating the size of target groups, sharing lessons learned based on

  consistent definitions, and allocating resources appropriately. A

  literature review was conducted to determine what formal definitions of

  hard-to-reach populations exist and how they are being used, and to

  propose definitions to consider for future use. Overall, we found that

  (1) there is a need to distinguish populations that are hard to reach

  versus hard to vaccinate, and (2) the existing literature poorly defined

  these populations and clear criteria or thresholds for classifying them

  were missing. Based on this review, we propose that hard-to-reach

  populations be defined as those facing supply-side barriers to

  vaccination due to geography by distance or terrain, transient or

  nomadic movement, healthcare provider discrimination, lack of healthcare

  provider recommendations, inadequate vaccination systems, war and

  conflict, home births or other homebound mobility limitations, or legal

  restrictions. Although multiple mechanisms may apply to the same

  population, supply-side barriers should be distinguished from

  demand-side barriers. Hard-to-vaccinate populations are defined as those

  who are reachable but difficult to vaccinate due to distrust, religious

  beliefs, lack of awareness of vaccine benefits and recommendations,

  poverty or low socioeconomic status, lack of time to access available

  vaccination services, or gender-based discrimination. Further work is

  needed to better define hard-to-reach populations and delineate them

  from populations that may be hard to vaccinate due to complex refusal

  reasons, improve measurement of the size and importance of their impact,

  and examine interventions related to overcoming barriers for each

  mechanism. This will enable policy makers, governments, donors, and the

  vaccine community to better plan interventions and allocate necessary

  resources to remove existing barriers to vaccination. (C) 2019 Elsevier

  Ltd. All rights reserved.'
affiliation: 'Ozawa, S (Corresponding Author), UNC Eshelman Sch Pharm, CB 7574,Beard
  Hall 115H, Chapel Hill, NC 27599 USA.

  Ozawa, Sachiko; Yemeke, Tatenda T., Univ N Carolina, UNC Eshelman Sch Pharm, Div
  Practice Adv \& Clin Educ, Chapel Hill, NC 27515 USA.

  Ozawa, Sachiko, Univ N Carolina, UNC Eshelman Sch Pharm, Dept Maternal \& Child
  Hlth, Chapel Hill, NC 27515 USA.

  Evans, Daniel R., Duke Univ, Sch Med, Durham, NC USA.

  Pallas, Sarah E.; Wallace, Aaron S., CDC, US Ctr Dis Control \& Prevent, Global
  Immunizat Div, Atlanta, GA USA.

  Lee, Bruce Y., Johns Hopkins Bloomberg Sch Publ Hlth, Publ Hlth Computat \& Operat
  Res PHICOR, Baltimore, MD USA.

  Lee, Bruce Y., Johns Hopkins Bloomberg Sch Publ Hlth, Dept Int Hlth, Baltimore,
  MD USA.

  Lee, Bruce Y., Johns Hopkins Univ, GOPC, Baltimore, MD USA.'
author: Ozawa, Sachiko and Yemeke, Tatenda T. and Evans, Daniel R. and Pallas, Sarah
  E. and Wallace, Aaron S. and Lee, Bruce Y.
author-email: ozawa@unc.edu
author_list:
- family: Ozawa
  given: Sachiko
- family: Yemeke
  given: Tatenda T.
- family: Evans
  given: Daniel R.
- family: Pallas
  given: Sarah E.
- family: Wallace
  given: Aaron S.
- family: Lee
  given: Bruce Y.
da: '2023-09-28'
doi: 10.1016/j.vaccine.2019.06.081
eissn: 1873-2518
files: []
issn: 0264-410X
journal: VACCINE
keywords: Hard-to-reach; Definition; Vaccination; Immunization; Unvaccinated
keywords-plus: 'HUMAN-PAPILLOMAVIRUS VACCINATION; ROUTINE IMMUNIZATION COVERAGE;

  MIDDLE-INCOME COUNTRIES; HEALTH-CARE; INFLUENZA VACCINATION; CHILDREN;

  BARRIERS; RECOMMENDATIONS; INCREASE; SERVICES'
language: English
month: SEP 3
number: '37'
number-of-cited-references: '106'
orcid-numbers: 'Ozawa, Sachiko/0000-0001-7608-9038

  Evans, Daniel/0000-0002-9818-5001

  Wallace, Aaron/0000-0003-2264-3229

  Pallas, Sarah/0000-0002-9719-6278

  Yemeke, Tatenda/0000-0002-1489-627X'
pages: 5525-5534
papis_id: 91faa1a429daf4ac7e6bfc12c827df4e
ref: Ozawa2019defininghardtoreach
researcherid-numbers: 'Ozawa, Sachiko/Z-4944-2019

  '
tags:
- review
times-cited: '36'
title: Defining hard-to-reach populations for vaccination
type: article
unique-id: WOS:000485212400005
usage-count-last-180-days: '3'
usage-count-since-2013: '16'
volume: '37'
web-of-science-categories: Immunology; Medicine, Research \& Experimental
year: '2019'