A Systems-Based Framework for Immunisation System Design: Six Loops, Three Flows, Two Paradigms

Figures & data

Table 1. Overview of stakeholder interaction activities that served as input for IMS diagram development. The numbers of the activities (1a to 7d) listed in this table appear in Figure 1.

Interaction type		Qualitative research method	Participants, location, timing	Main topics discussed
1	Exploration global level	Stakeholder interviews, conference workshops	1a MSF, Brussels 1b UNICEF, SC division, Copenhagen 1 c Vaccine manufacturers 1d Donor organisations 2015–2019	Links between Health system development and humanitarian aid, infrastructure gap, skills retention, project handover Vaccine funding, humanitarian mechanisms, vaccine stockpiles Health systems strengthening approach UNICEF, GAVI Improvement potential at interfaces of disciplines, e.g., vaccine manufacturing & procurement conditions, temperature requirements
2	Mental model elicitation national immunisation system	Group model building	Senior and middle EPI staff national level. Mixed groups: Kigali 2016: 22 participants from Rwanda, Kenya, Uganda, Tanzania, South-Sudan Nairobi 2017: 25 participants from Rwanda, Kenya, Uganda, Burundi, Tanzania, South-Sudan	Stakeholders involved in execution and decision making Mental model change from Supply Chain to systems thinking Policy making in cMYP, immunisation plan Private sector role and partnerships (logistics) Sharing views between countries, adapt approach to country Financial mechanisms, equity, sustainability, efficiency Data management and issues, denominator error Vaccine coverage and health outcomes: delays, epidemiology Implementation complexity: new vaccines, eLMIS Workforce capacity, immunisation integration in health services
3	Mental model elicitation district level	Interviews, observation, numerical data collection at DHs	Rwanda: 2 district hospitals (2018–2019) Kenya: 2 district hospitals (2018)	Vaccine supply chain, vaccine wastage, ordering process Outreach planning and funding Skills and training EPI staff and Community Health Workers Diversity between HCs in the district, root causes of coverage variation Demand data availability, district coordinating role
4	Mental model elicitation local level	Interviews, observations, numerical data collection at HCs, outreach, CHWs	Kenya: 5 health facilities (2018) Rwanda: 5 health facilities (2019)	Local vaccine management organisation, vaccine transport Community health worker, defaulter tracing, disease case detection Demand-side determinants, access to HFs Impact of local problem-solving capacity at HF
5	Validation national level IMS model	Feedback workshops	EPI, WHO, implementers Nairobi 2018, Kigali 2019	Data management Public-Private health services
6	Validation national level IMS model	Feedback meetings	EPI, Kigali, 2019 UNICEF, Kigali, 2019	Financial sustainability Supply chain redesign, Digital transformation Disease surveillance, emergency immunisation (measles, Ebola) Integration with other preventive HC systems (nutrition, Primary HC)
7	Validation and refinement by international domain experts	Feedback meetings (2019)	7a Academic anthropologist 7b Funding mechanism expert 7 c Academic Public Health 7d Academic systems expert	Vaccine hesitancy, emergency immunisation Design thinking, paradigm shift, Innovation interventions Sustainable mechanisms, Local contextual approach, community health Sustainability and resilient systems, systems levels and interventions

Figure 1. Map of interaction activities with stakeholders for the development and validation of the systems diagram. The numbers 1a,b,c to 7 a,b,c refer to the stakeholder engagement activities listed in Table 1, e.g., 1a is a stakeholder interview with Médecins sans Frontières in Brussels. The concentric rings, with the resulting IMS diagram in the centre, indicate the system levels at which the stakeholder operates, or has his or her expertise. The four outer orientations (Vaccine supply, Humanitarian operations, Immunisation demand and Healthcare system) refer to the main background of the stakeholders. One activity can appear at different locations, for example, a group model building session with stakeholders with different backgrounds. The grey arrows show the iterative, multi-level knowledge build-up while the black arrows indicate how this knowledge flows to and from the IMS diagram under construction.

Figure 2. Aggregated system diagram highlighting two paradigms: planned and emergency immunisation.

Figure 3. Three flows that need to be synchronised for high IMS performance, make up the focal point of the IMS: Child (Population wellbeing), Nurse (Workforce & infrastructure), and Vaccine (Vaccine distribution).

Table 2. Brief explanation of the feedback loops in the IMS diagram. A detailed explanation can be found in Annexe 1.

R1 population wellbeing loop Vaccination – Population health status – Population wellbeing – Vaccination	Vaccination improves Population health status over time which increases Population wellbeing. Higher wellbeing leads to higher access to vaccination.
R2 Workforce and infrastructure loop Vaccination – Population health status – Immunisation plan – Workforce & infrastructure – Vaccination	Vaccination improves immunisation coverage levels leading to less vaccine-preventable disease cases and higher Population health status over time. Higher Population health status requires less resources for catch-up immunisation, and more room for improving immunisation services (e.g., by increasing workforce skills and capacity) and their coverage (e.g., with outreach services) which both take several years to effectively impact vaccination services.
R3 Vaccine supply loop Vaccination – Population health status – Immunisation plan – and infrastructure – Vaccination	Vaccination improves immunisation coverage levels leading to less vaccine-preventable disease cases and higher Population health status over time. Higher Population health status requires less resources for catch-up immunisation, and leaves room for expanding the schedule with additional vaccines (e.g., against HPV, COVID-19) or booster doses throughout the population’s lifetime to further reduce the national burden of disease and to respond to evolving epidemiology.
B1 Outbreak prevention loop Vaccination – Population health status – Population at risk – Surveillance & response – Vaccination	Vaccination improves protection against vaccine-preventable diseases (VPDs) and Population health status which reduces the Population at risk of getting VPDs. A higher Population at risk leads to more disease cases that need to be identified via surveillance systems and more execution of response immunisation campaigns to prevent outbreaks. More campaigns lead to more vaccinations.
R4 Outbreak loop Population health status – Population at risk – Outbreak – Morbidity and mortality – Population health status	Lower Population health status increases Population at risk of getting a vaccine preventable disease. Higher Population at risk increases the probability and size of Outbreaks which increase Morbidity and mortality numbers due to the VPD. These numbers directly reduce Population health status indicators.
B2 Outbreak response loop Vaccination – Population health status – Population at risk – Outbreak – Outbreak response immunisation – Vaccination	Lower Vaccination reduces Population health status over time and increases Population at risk. Higher Population at risk increases the probability and size of Outbreaks which require more Outbreak response immunisation, which manages to increase Vaccination.

Figure 4. IMS diagram: Aggregated causal-loop diagram of IMS in a LMIC. Applicable to national, subnational level and local settings.

Figure 5. Stakeholders mapped on the generic LMIC IMS diagram.

Figure 6. System assessment of local settings derived from cases in Rwanda: rural area (top) and peri-urban area (bottom) with respect to measles. Mechanisms that are active, are shown as red or green loops when they have a, respectively, negative or positive impact on the IMS performance. Mechanisms that are not active at the moment of assessment, such as international emergency immunisation mechanisms (B2), are shown as black loops on the IMS model.

Figure 7. Factors determining sustainability of the IMS: endogenous factors (green) and exogenous factors (blue). Exogenous resilience factors of the IMS are red.

Table 3. Examples of immunisation system leverage points classified according to Malhi et al. (2009) based on Meadows (1989).

Intervention level	IMS Leverage points and potential directions of change
1. Paradigm	Expanding the mindset behind the IMS: from the anthropocentric ethic of preventive health as an enabler for human wellbeing, to the One Health/Planetary Health concept: Multi-stakeholder health approach (human, animal, environment) (Whitmee et al., 2015) Emergence instead of centrally controlled system: Social cohesion as cornerstone of health-seeking behaviour (Ubuntu) (Barugahare, 2018)
2. Goals	Complement IMS targets based on SDG3, IHRs and national immunisation targets with targets addressing Vulnerable groups and geographic diversity Sustainability targets beyond financial sustainability Differentiation based on transdisciplinary thinking
3. System structure (across IMS loops and outside IMS)	Self-Organising power Country-specific IMS, adapted to local circumstances Self-Organisation at subnational level: counties, districts, health centres
	Rules of the system Planned and emergency immunisation as one holistic system Synchronisation at vaccination point: differentiation, effectiveness, efficiency Community engagement, CHWs connecting immunisation demand and supply National immunisation programme adequacy and funding sustainability
	Information flows Patient-based data, real-time vulnerability maps available to health workers Patient-based health information available to population for fostering personal and community health engagement Supply-related data available to relevant stakeholders
4. Feedback and delays	Reinforcing feedback loops Efficiency of vaccine supply loop: vaccine wastage reduction Efficiency and effectiveness of workforce and infrastructure loop Strength of wellbeing loop, linked to education and poverty Balancing feedback loops Outbreak prevention loop strength: ability of surveillance and response Interface between national and international response to epidemics Delays Immunisation delivery options with different dynamics: RI, campaigns Delays in outbreak prevention loop and outbreak response loop Synchronisation of vaccine supply and distribution delays to create stability in the system
5. Structural elements (within IMS loops)	Vaccine Supply chain network layout Size of warehouses and vaccine inventory levels Workforce capacity

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