Table 6 Sustainability challenges and selected references from Cat2 papers

 Vaccine acceptance

HPV vaccination: cultural acceptance, reaching girls at age of high absenteeism, education about HPV vaccines [70]

[71,72,73,74,75,76,77]

 Community engagement

For eradication of polio [78]

Measles elimination after COVID-19 pandemic [79]

[80,81,82,83,84,85,86,87,88,89]

Impact of functioning health system and stable communities [90]

 Socio-economic determinants of health

[91]

Electrical infrastructure investments needed for UHC [92]

[23, 26, 93]

Migrating populations: Mixing of under-immunized with higher immunized populations in Turkey-Syria [94]

 Measuring performance, Data for health

[13, 69, 95,96,97,98,99].

 Political commitment

Investments for health systems strengthening [21]

Political endorsement and communication for vaccination. E.g., HPV vaccination [71, 90]

 Need for systems thinking to connect interventions with SDG3 and other SDGs

[14, 62, 74, 75, 100,101,102,103,104,105,106,107,108]

 New vaccine introduction and vaccination coverage

[22, 76, 109,110,111,112,113]

NITAG decision support, absence of reliable burden of disease data [114]

 Disease elimination and eradication

Behavioral challenges of strict polio strategies near eradication [59, 115, 116]

 UHC and equity

Universal primary health care instead of disease-specific programs [21]

[117,118,119,120,121,122,123].

health insurance [124]

Need for Global Health Diplomacy to promote SDG10 as IHR were violated with COVID-19 [125]

 Decision making

Decentralized decision making [13, 109, 126,127,128,129,130]

Applying Health Technology Assessment for universal health coverage [131]

 Resilience and preparedness

[132,133,134,135]

Sustainability of health system through strengthening immunization, COVID-19 pandemic [136]

 Collaboration

[43, 54, 82, 137,138,139,140,141,142,143]

Cross-country collaboration for disease prevention, e.g. cross-border Health Initiative in Kenya and Somalia [144]

 Donor funding dependency

Dependency on development partner support [76, 107, 108, 145,146,147,148,149,150,151,152]

In SSA the effect of ODA on under-five mortality is higher than elsewhere [153]

 Transitioning out of donor funding

Transitioning out of donor funding or emergency funding [154,155,156,157,158,159]

Difficulty of finding reliable data on budget and execution poses an issue for financial sustainability [160]

Creating fiscal sustainability and efficiency [108, 124, 146, 148, 156, 161,162,163,164]

 Capacity building, accountability, commitment

[13, 46, 82, 99, 126, 149, 163, 165,166,167,168,169,170,171,172]

Technical support, open data (GIS), and supportive supervision for surveillance and disease eradication (Polio) [173]

Health worker motivation and resilience [174,175,176]

 Health Information Systems

[13, 72, 177,178,179,180,181]

Home-based records must be user-centered and appropriate for local burdens of disease [182]

Improvement of data quality is needed at the HC level related to staff but investments are usually at higher levels and in technology [183]

Data collection, disease surveillance, Electronic health records [13, 93, 171, 184,185,186,187,188,189,190]

 Vaccine supply chain data

Security through traceability, e.g., barcoding, GS1 [191]

 Burden of disease evidence for decisions

[67, 69, 114, 123]

 Data exchange systems and training

[13, 82, 121, 126, 149, 172]

 Vaccine distribution

Challenges of vaccine supply chains in LMICs [13, 19, 76, 107, 163, 168, 192,193,194,195,196,197,198,199]

Technical innovations that lead to unaffordable transportation costs are not sustainable, e.g. vaccine direct delivery in Nigeria [200]

 Vaccine availability to LMICs

[13, 201,202,203,204,205,206,207,208,209]

Vaccine manufacturers from emerging countries. Need for good pharmacovigilance practice to build trust in vaccines [33], need for traceability, stockpiling and new packaging technologies [191, 210]

Structural dependency of countries on global vaccine manufacturers, e.g. Brasil [211]

 New vaccine development

[13, 63, 97, 106, 111, 212,213,214,215,216,217,218,219,220]

NTDs: Need for incentives for development of vaccines for the poor [221,222,223]

Packaging development for increasing coverage [224]

 Implementation barriers and need for tailored solutions

Tailored solutions

Acknowledging implementation barriers and developing strategies [25, 48, 58, 67, 79, 117,118,119, 225,226,227,228,229,230]

 Integrated delivery platform

[70, 76, 127, 186, 189, 231,232,233,234,235,236]

Implementation design equally important as intervention design [66]

Public-private partnerships for community health [237]

 Continuity

[63, 65, 175, 213, 238,239,240,241]

 Resilience in service delivery

[100, 172, 242,243,244,245,246,247]

Effect of conflict on performance of childhood vaccination [133]

Effect of outbreaks on ongoing health prevention [248]