System within systems: challenges and opportunities for the Expanded Programme on Immunisation in Pakistan

Universal health coverage in Pakistan: exploring the landscape of the health system, health seeking behaviours, and utilization of health services

The attainment of the noble objective of Universal Health Coverage (UHC)- 'leaving no one behind' necessitates sufficient financial resources, an ample supply of skilled healthcare professionals, and the availability of essential services as part of a basic package This paper presents an analysis of the health system, health seeking behaviours and health service utilization en route to UHC in Pakistan. We have used the UHC 14 tracer indicators of service coverage to see where Pakistan stands, what are the gaps and what needs to be done. Pakistan clearly is lagging behind its neighboring countries. The country's health system ought to work on health seeking behaviours and broader determinants of health. The pursuit of UHC demands a shared responsibility and collective action, with stakeholders from different sectors uniting their efforts and expertise. Together, they can establish robust systems, design comprehensive policies, allocate adequate resources, and implement interventions that transcend disciplinary boundaries.

Vaccine Trends in Pakistan: A Review of Immunization Challenges and Setbacks Prompted by Inadequate Disaster Management

Pakistan bears an incredible burden of vaccine-preventable diseases, and efforts to improve widespread immunization have been hindered by inadequate public health management following disasters and other health emergencies. Through a brief review of Pakistan's health system, an understanding of routine immunization challenges is sought based on the organizational changes made to the planning and delivery of immunization activities. Further, recent immunization trends of measles, polio, and tuberculosis are examined in correspondence to health emergencies prompted by climate change and the COVID-19 pandemic. The national public health response to each disease is discussed, and insight is given to how the devolution of Pakistan's health system may have influenced the severity of each emergency. Focus is given to the potential immunization challenges and how they may impact future initiatives for the control of vaccine-preventable diseases. Although incidence rates suggest increased cases of certain vaccine-preventable diseases and disruptions of immunization activities following recent disasters, further studies may need to be conducted to establish a stronger understanding of the immunization trends noted within this review.

Exploring the reasons for defaulting from childhood immunization: a qualitative study in Pakistan

BACKGROUND

Childhood vaccination is widely recognized as the most effective means to prevent various diseases. However, a considerable amount of children still miss out on their vaccination schedules. Therefore, this study explores the reasons for defaulting from the expanded program on immunization in district Swat, Pakistan.

METHODS

A qualitative phenomenological approach was used. Data collection took place from March to September 2022. Thirty-six in-depth interviews were conducted with participants who had defaulter children. The collected qualitative data were analysed thematically to identify key patterns and themes related to the reasons for defaulting from childhood vaccination schedules.

RESULTS

Six themes emerged, i.e., illness of the defaulter child at the scheduled time, perceived side effects of the vaccination, factors related to caregivers, myths and misconceptions, vaccinators attitudes and crowed vaccination centres, as well as poor immunization service arrangements. Four subthemes arose related to caregivers, such as lack of clear understanding about completion of vaccination, least priority for child's vaccination, cultural restriction on mothers, and the loss of vaccination card.

CONCLUSION

According to the study's findings, caregivers have their own perceptions regarding the non-completion of their children's vaccination schedule. The childhood immunization defaulting arises from various factors including child illness, Adverse Events Following Immunization (AEFIs) concerns, misconceptions, improper injection techniques, and negative vaccinator attitudes. The vaccination completion rate may be increased if the concerns of the caregivers are appropriately addressed.

Interventions to improve vaccine coverage of pregnant women in Aotearoa New Zealand

Introduction Maternal vaccination against influenza and pertussis protects mothers and babies from severe disease and is recommended and funded in Aotearoa New Zealand. Despite this, maternal vaccination uptake is low, varies by region and is inequitable, with Māori and Pacific māmā (mothers) less likely to receive vaccination. Aim To determine what interventions currently exist to support and encourage maternal vaccination against influenza and pertussis and what changes and interventions could be implemented to improve coverage, with a focus on Māori and Pacific hapū māmā (pregnant mothers). Methods Interviews with six participants with diverse roles in the vaccination workforce were conducted. Participants were involved in education, certification and supporting vaccinators, high-level strategising, and vaccination. Interviews aimed to determine what interventions currently exist for hapū māmā, what changes need to be made to improve coverage and how Māori and Pacific people have been specifically engaged. Qualitative data analysis was used to determine themes. Results Participants identified that interventions must focus on prioritising and emphasising the importance of maternal vaccination, promoting collaboration and innovation, making interventions accessible, and empowering Māori- and Pacific-driven avenues to vaccination. To create positive foundations, participants identified the importance of building and maintaining trust and affording mothers' time and autonomy in vaccination. Discussion Healthcare professionals need to proactively engage hapū māmā about vaccination and collaborate in service delivery. Interventions must be suitably accessible and allow for the autonomy of hapū māmā over vaccination decisions. Equity should be considered at the foundation of vaccine interventions to improve the accessibility of vaccines to all communities.

Community centred co-design methodology for designing and implementing socio-behavioural interventions to counter COVID-19 related misinformation among marginalized population living in the squatter settlements of Karachi, Pakistan: a methodology paper

BACKGROUND

Misinformation regarding COVID-19 pandemic and vaccination is damaging COVID-19 vaccine trust and acceptance in Low- and Middle-Income Countries (LMIC). Identification of misinformation and designing locally acceptable solutions are needed to improve COVID-19 vaccine acceptance. This study aimed to utilize community-led co-design methodology to evaluate misinformation regarding COVID-19 and develop contextual interventions to address misinformation in a marginalized peri urban slum communities of Landhi town Karachi, Pakistan.

METHODS

This study was conducted between January and December 2021, in marginalized peri-urban slum dwellers of Muslimabad Colony, Landhi Town Karachi, Pakistan. We used a community-centred co-design methodology embedded within mixed study design to identify misinformation, co-design, test and implement locally acceptable solutions. The co-design methodology involved five stages of the design thinking model: (1) Empathize, (2) Define, (3) Ideate, (4) Prototype, and (5) Test. The project involved active engagement and participation of wide range of stakeholders and community beneficiaries (end users) including local EPI vaccinators, informal healthcare workers, religious leaders (male and female), schoolteachers (male and female), local government representatives, community leaders, housewives, youth, and general population. To develop a trusting relationship, and understand local culture, values, practices, and traditions, we allowed one month of observation period (observe, engage, watch, and listen) in the beginning, followed by door-to-door survey along with focus group discussions (FGD) and in-depth interviews (IDI) at baseline. Co-design workshops (separate for male and female) were conducted at each stage of co-design methodology to design and test locally acceptable solutions.

CONCLUSION

Community-centred co-design methodology was not only successful in designing, testing, and evaluating locally acceptable solutions but it also actively engaged and empowered the marginalized population living in peri urban slum communities of Karachi, Pakistan.

Differential coverage for vaccines in the expanded program on immunization (EPI) among children in rural Pakistan

BACKGROUND

Pakistan has a well-established Expanded Program on Immunization (EPI) however vaccine-preventable diseases still account for high infant and child mortality rates. This study describes the differential vaccine coverage and determinants of vaccine uptake in rural Pakistan.

METHODS

From October 2014 to September 2018, we enrolled children younger than 2 years of age from the Matiari Demographic Surveillance System in Sindh, Pakistan. Socio-demographic and vaccination history were collected from all participants. Vaccine coverage rates and timeliness were reported. Socio-demographic variables for missed and untimely vaccination were studied in multivariable logistic regression.

RESULTS

Of the 3140 enrolled children, 48.4 % received all EPI recommended vaccines. Only 21.2 % of these were age appropriate. Around 45.4 % of the children were partially vaccinated, and 6.2 % were unvaccinated. Highest coverage was seen for the first dose of pentavalent (72.8 %), 10-valent Pneumococcal Conjugate Vaccine (PCV10) (70.4 %) and Oral Polio Vaccine (OPV) (69.2 %) and the lowest coverage was for measles (29.3 %) and rotavirus (1.8 %) vaccines. Primary caretakers and wage earners with a higher level of education were protective against missed and untimely vaccination. Enrollment in the 2nd, 3rd and 4th study year was negatively associated with being unvaccinated whereas distance from a major road was positively associated with non-adherence to schedule.

CONCLUSION

Vaccine coverage was low among children in Matiari, Pakistan, and majority received delayed doses. Parents' education status and year of study enrollment was protective against vaccine dropout and delayed vaccination whereas geographical distance from a major road was a predictor. Vaccine promotion and outreach efforts may have had a beneficial impact on vaccine coverage and timeliness.

What are the barriers and facilitators to polio vaccination and eradication programs? A systematic review

Global efforts to eradicate polio by the Global Polio Eradication Initiative agency partners and country-level stakeholders have led to the implementation of global polio vaccination programs. This study presents the findings of existing studies regarding the barriers and facilitators that countries face when implementing polio interventions. A comprehensive search was conducted in OVID Medline, OVID Embase, EBSCO CINAHL Plus, and Web of Science. Eligible studies underwent quality assessment. A qualitative evidence synthesis approach was conducted and aligned to the Consolidated Framework for Implementation Research (CFIR). The search identified 4147 citations, and following the removal of duplicates and screening according to our inclusion/exclusion criteria, 20 articles were eligible for inclusion in the review. Twelve countries were represented in this review, with India, Nigeria, Pakistan, Ethiopia, and Afghanistan having the most representation of available studies. We identified 36 barriers and 16 facilitators. Seven themes emerged from these barriers and facilitators: fear, community trust, infrastructure, beliefs about the intervention, influential opinions, intervention design, and geo-politics. The most frequently cited CFIR constructs for the facilitators and barriers were knowledge and beliefs about the intervention, followed by available resources. This study identified a wide range of barriers and facilitators to polio vaccination implementation across the globe, adding to the scarce body of literature on these barriers and facilitators from an implementation perspective and using a determinant framework. The diversity of factors among different groups of people or countries highlights the relevance of contexts. Implementers should be conversant with the contexts within which polio eradication programs boost intervention coverage and capacity. This study provides policymakers, practitioners, and researchers with a tool for planning and designing polio immunization programs. Trial registration: A protocol for this systematic review was developed and uploaded onto the PROSPERO international prospective register of systematic reviews database (Registration number: CRD42020222115).

Determinants of vaccine coverage and timeliness in a northern Pakistani village

The incidence of vaccine preventable disease in Pakistan remains high despite a long-standing Expanded Program on Immunization (EPI). We describe vaccine completeness, timeliness and determinants of coverage from a remote rural cohort (2012–2014). Vaccination histories were taken from EPI records. Vaccination was complete if all doses were received according to the EPI schedule and timely if doses were not ≥3 days early or ≥ 28 days late. Three models are presented: a multivariable logistic regression of household demographic and socioeconomic factors associated with complete vaccination, a multivariable mixed effects logistic regression assessing whether or not the vaccine was administered late (versus on-time), and a mixed effects multivariable Poisson regression model analysing the interval (in days) between vaccine doses. Of 959 enrolled children with full vaccination histories, 88.2 and 65.1% were fully vaccinated following either the pentavalent or DPT/HBV schedules if measles was excluded; coverage dropped to 50.0 and 27.1% when both doses of measles were included. Sixty-four (6.7%) were unvaccinated. Coverage and timeliness declined with subsequent doses. Migrating into the village after 1995 (95%CI 1.88 to 5.17) was associated with late vaccination. Being male, having an older father, and having parents with at least some formal education reduced the likelihood of a late dose. The interval between doses was consistent at 5 weeks (compared with the 4 weeks recommended by EPI). None of the socio-demographic variables were related to the likelihood of receiving full coverage. Vaccine coverage in Oshikhandass was higher than national averages. Measles vaccine coverage and timeliness were low; special consideration should be paid to this vaccine. The local vaccination schedule differed from the EPI, but the consistency suggests good local administration.

Usability and Acceptability of a Mobile App for Behavior Change and to Improve Immunization Coverage among Children in Pakistan: A Mixed-Methods Study

Background: Pakistan’s immunization uptake rates are still significantly lower than anticipated despite several initiatives. Lack of awareness, forgetting about vaccination schedule, and vaccine misconception/misinformation are a few of the major drivers that mitigate the rates of immunization. The current COVID-19 pandemic emphasizes the importance of immunization. The significant reductions in regular childhood vaccination during pandemic have increased the risk of outbreaks of vaccine-preventable diseases. Concerns among parents over possibly exposing their children to COVID-19 during child visits may have contributed to the reported declines. Innovative and cost-effective mHealth interventions must be implemented in order to address the problem of inadequate immunization rates. In addition, it is also critical to understand the end user needs in order to reflect on the highly relevant essence of the customized healthcare experience. Objective: The aim of this study was to learn about caregivers’ attitudes toward the usability and acceptability of behavior-change smartphone applications (mobile phones) for improving immunization coverage in Pakistan. Methods: A mixed-method design was employed for this study. The study was conducted at Aga Khan University, Hospital. Parents visiting the Community Health Center for 6-week vaccination of their children were recruited. The study was conducted in two stages. Stage 1 consisted of qualitative interviews that grasped the parent’s attitudes and challenges to immunization, as well as their acceptability and accessibility of the smartphone-based behavior-change application to increase vaccine uptake. Stage 1 was followed by stage 2, in which data were collected through a questionnaire designed by using data from qualitative interviews. Results: The majority of participants agreed that immunization serves an important role in protecting their child from illnesses that cause morbidity and mortality. Almost all of them emphasized the importance of using a pre-appointment method at vaccination center in order to reduce the waiting time. Furthermore, participants were also interested in AI-based behavior modification applications related to immunization. They also wanted to have applications in their native language for better understanding and communication of related information. In our study, approximately 95.2 percent of participants agreed to accept SMS immunization updates, which was also reasonably high. Lastly, the majority of them identified forgetfulness as a significant contributor to regular immunization. Conclusion: To enhance the uptake of childhood vaccines, overall vaccination rates, and overcome barriers related to vaccination coverage, cost-effective and user-friendly mHealth AI-based smart phone applications are required to raise awareness regarding the continuation of vaccination service and the importance of timely vaccination. Parents’ experiences and attitudes must be considered while designing and evaluating the efficacy of mHealth-based interventions.

Advancing sustainable development goals through immunization: a literature review

BACKGROUND

Immunization directly impacts health (SDG3) and brings a contribution to 14 out of the 17 Sustainable Development Goals (SDGs), such as ending poverty, reducing hunger, and reducing inequalities. Therefore, immunization is recognized to play a central role in reaching the SDGs, especially in low- and middle-income countries (LMICs). Despite continuous interventions to strengthen immunization systems and to adequately respond to emergency immunization during epidemics, the immunization-related indicators for SDG3 lag behind in sub-Saharan Africa. Especially taking into account the current Covid19 pandemic, the current performance on the connected SDGs is both a cause and a result of this.

METHODS

We conduct a literature review through a keyword search strategy complemented with handpicking and snowballing from earlier reviews. After title and abstract screening, we conducted a qualitative analysis of key insights and categorized them according to showing the impact of immunization on SDGs, sustainability challenges, and model-based solutions to these challenges.

RESULTS

We reveal the leveraging mechanisms triggered by immunization and position them vis-à-vis the SDGs, within the framework of Public Health and Planetary Health. Several challenges for sustainable control of vaccine-preventable diseases are identified: access to immunization services, global vaccine availability to LMICs, context-dependent vaccine effectiveness, safe and affordable vaccines, local/regional vaccine production, public-private partnerships, and immunization capacity/capability building. Model-based approaches that support SDG-promoting interventions concerning immunization systems are analyzed in light of the strategic priorities of the Immunization Agenda 2030.

CONCLUSIONS

In general terms, it can be concluded that relevant future research requires (i) design for system resilience, (ii) transdisciplinary modeling, (iii) connecting interventions in immunization with SDG outcomes, (iv) designing interventions and their implementation simultaneously, (v) offering tailored solutions, and (vi) model coordination and integration of services and partnerships. The research and health community is called upon to join forces to activate existing knowledge, generate new insights and develop decision-supporting tools for Low-and Middle-Income Countries' health authorities and communities to leverage immunization in its transformational role toward successfully meeting the SDGs in 2030.

Assessing community engagement in Nigeria polio eradication initiative: application of the Consolidated Framework for Implementation Research

OBJECTIVE

This study employed the Consolidated Framework for Implementation Research (CFIR) to assess factors that enhanced or impeded the implementation of community engagement strategies using the Nigerian polio programme as a point of reference.

DESIGN

This study was a part of a larger descriptive cross-sectional survey. The CFIR was used to design the instrument which was administered through face-to-face and phone interviews as well as a web-based data collection platform, Qualtrics.

SETTING

The study took place in at least one State from each of the six geopolitical zones in Nigeria (Nasarawa, Borno, Kano, Sokoto, Anambra, Bayelsa, Lagos, Ondo and Oyo States as well as the Federal Capital Territory).

PARTICIPANTS

The respondents included programme managers, policy-makers, researchers and frontline field implementers affiliated with the Global Polio Eradication Initiative (PEI) core partner organisations, the three tiers of the government health parastatals (local, state and federal levels) and academic/research institutions.

RESULTS

Data for this study were obtained from 364 respondents who reported participation in community engagement activities in Nigeria's PEI. Majority (68.4%) had less than 10 years' experience in PEI, 57.4% were involved at the local government level and 46.9% were team supervisors. Almost half (45.0%) of the participants identified the process of conducting the PEI program and social environment (56.0%) as the most important internal and external contributor to implementing community engagement activities in the community, respectively. The economic environment (35.7%) was the most frequently reported challenge among the external challenges to implementing community engagement activities.

CONCLUSION

Community engagement strategies were largely affected by the factors relating to the process of conducting the polio programme, the economic environment and the social context. Therefore, community engagement implementers should focus on these key areas and channel resources to reduce obstacles to achieve community engagement goals.

Systematic review of the costs for vaccinators to reach vaccination sites: Incremental costs of reaching hard-to-reach populations

INTRODUCTION

Economic evidence on how much it may cost for vaccinators to reach populations is important to plan vaccination programs. Moreover, knowing the incremental costs to reach populations that have traditionally been undervaccinated, especially those hard-to-reach who are facing supply-side barriers to vaccination, is essential to expanding immunization coverage to these populations.

METHODS

We conducted a systematic review to identify estimates of costs associated with getting vaccinators to all vaccination sites. We searched PubMed and the Immunization Delivery Cost Catalogue (IDCC) in 2019 for the following costs to vaccinators: (1) training costs; (2) labor costs, per diems, and incentives; (3) identification of vaccine beneficiary location; and (4) travel costs. We assessed if any of these costs were specific to populations that are hard-to-reach for vaccination, based on a framework for examining supply-side barriers to vaccination.

RESULTS

We found 19 studies describing average vaccinator training costs at $0.67/person vaccinated or targeted (SD $0.94) and $0.10/dose delivered (SD $0.07). The average cost for vaccinator labor and incentive costs across 29 studies was $2.15/dose (SD $2.08). We identified 13 studies describing intervention costs for a vaccinator to know the location of a beneficiary, with an average cost of $19.69/person (SD $26.65), and six studies describing vaccinator travel costs, with an average cost of $0.07/dose (SD $0.03). Only eight of these studies described hard-to-reach populations for vaccination; two studies examined incremental costs per dose to reach hard-to-reach populations, which were 1.3-2 times higher than the regular costs. The incremental cost to train vaccinators was $0.02/dose, and incremental labor costs for targeting hard-to-reach populations were $0.16-$1.17/dose.

CONCLUSION

Additional comparative costing studies are needed to understand the potential differential costs for vaccinators reaching the vaccination sites that serve hard-to-reach populations. This will help immunization program planners and decision-makers better allocate resources to extend vaccination programs.

Progress on the national action plan of Pakistan on antimicrobial resistance (AMR): a narrative review and the implications

Introduction: The emergence of antimicrobial resistance (AMR) is a threat to public health. In 2015, the World Health Organization (WHO) introduced a global action plan to tackle AMR in the World Health Assembly. Pakistan's national action plan (NAP) for AMR was released in May 2017 by the Ministry of National Health Services. Based on the NAP, strategies have been initiated on a national and provincial scale in Pakistan.Areas covered: This narrative review of the five components of the Pakistan NAP has been undertaken to discuss some of the challenges in implementation of the NAP for AMR in Pakistan including different opinions and views of key stakeholders, combined with suggestions on potential ways to reduce the burden of the AMR.Expert opinion: Going forward, healthcare authorities should focus on screening and monitoring of all the objectives of the NAP by establishing proper policies as well as promoting antimicrobial stewardship interventions and Infection prevention and control (IPC) practices. Overall, the comprehensive strengthening of the healthcare system is required to adequately implement the NAP, tackle continued inappropriate antimicrobial use and high AMR rates in Pakistan.

Eradicating polio in Pakistan: a systematic review of programs and policies

Introduction: Established in 1994, Pakistan's polio program demonstrated early success. However, despite over 120 supplementary immunization activities in the last decade, polio eradication efforts in Pakistan have been unable to achieve their objective of halting polio transmission. Variable governance, and inconsistent leadership and accountability have hindered the success of the polio program and the quality of the campaigns. Insecurity and terrorism has interrupted polio activities, and community fears and misbeliefs about polio vaccinations continue to persist.Areas covered: The article consists of a systematic review of the barriers and facilitators associated with the delivery of polio eradication activities in Pakistan. We also provide a comprehensive review of the policy and programmatic decisions made by the Pakistan Polio Programme since 1994. Searches were conducted on Embase and Medline databases and 25 gray literature sources.Expert opinion: Polio eradication efforts must be integrated with other preventive health services, particularly immunization services. Addressing the underlying causes of polio refusals including underdevelopment and social exclusion will help counteract resistance to polio vaccination. Achieving polio eradication will require building health systems that provide comprehensive community-centered care, and improving governance and systems of accountability.

An Artificial Intelligence-Based, Personalized Smartphone App to Improve Childhood Immunization Coverage and Timelines Among Children in Pakistan: Protocol for a Randomized Controlled Trial

BACKGROUND

The immunization uptake rates in Pakistan are much lower than desired. Major reasons include lack of awareness, parental forgetfulness regarding schedules, and misinformation regarding vaccines. In light of the COVID-19 pandemic and distancing measures, routine childhood immunization (RCI) coverage has been adversely affected, as caregivers avoid tertiary care hospitals or primary health centers. Innovative and cost-effective measures must be taken to understand and deal with the issue of low immunization rates. However, only a few smartphone-based interventions have been carried out in low- and middle-income countries (LMICs) to improve RCI.

OBJECTIVE

The primary objectives of this study are to evaluate whether a personalized mobile app can improve children's on-time visits at 10 and 14 weeks of age for RCI as compared with standard care and to determine whether an artificial intelligence model can be incorporated into the app. Secondary objectives are to determine the perceptions and attitudes of caregivers regarding childhood vaccinations and to understand the factors that might influence the effect of a mobile phone-based app on vaccination improvement.

METHODS

A mixed methods randomized controlled trial was designed with intervention and control arms. The study will be conducted at the Aga Khan University Hospital vaccination center. Caregivers of newborns or infants visiting the center for their children's 6-week vaccination will be recruited. The intervention arm will have access to a smartphone app with text, voice, video, and pictorial messages regarding RCI. This app will be developed based on the findings of the pretrial qualitative component of the study, in addition to no-show study findings, which will explore caregivers' perceptions about RCI and a mobile phone-based app in improving RCI coverage.

RESULTS

Pretrial qualitative in-depth interviews were conducted in February 2020. Enrollment of study participants for the randomized controlled trial is in process. Study exit interviews will be conducted at the 14-week immunization visits, provided the caregivers visit the immunization facility at that time, or over the phone when the children are 18 weeks of age.

CONCLUSIONS

This study will generate useful insights into the feasibility, acceptability, and usability of an Android-based smartphone app for improving RCI in Pakistan and in LMICs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04449107; https://clinicaltrials.gov/ct2/show/NCT04449107.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/22996.

Defining hard-to-reach populations for vaccination

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 home-bound 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.