Vaccines are among the most effective public health interventions for reducing morbidity and mortality from infectious diseases, yet their effectiveness depends on maintaining vaccine potency throughout the cold chain from manufacture to administration. In many low- and middle-income countries, where disease burden is very high, weaknesses in cold chain systems continue to compromise immunisation programme performance and equitable access. Despite decades of investment, evidence indicates that cold chain failures remain common, yet the factors driving persistent gaps and the real-world impact of emerging innovations are not consistently synthesised. The objective of the review was to assess the major challenges affecting vaccine cold chain distribution in developing countries and to synthesise current evidence on technological and operational innovations aimed at addressing these constraints.

A narrative review methodology was employed, drawing on peer-reviewed literature and relevant grey literature published between 2008 and 2025. Searches were conducted in PubMed, Scopus and Google Scholar. Data were extracted and analysed thematically, focusing on logistical, infrastructural, workforce, geographic, economic, and policy-related dimensions of cold chain performance.

The review revealed persistent challenges, including unreliable electricity supply, inadequate storage and transport capacity, long distribution routes, limited funding for maintenance, fragmented governance and shortages of trained personnel. These factors contribute to temperature excursions, vaccine wastage and stock-outs, particularly in remote and underserved settings. Meanwhile, several innovations have demonstrated potential to strengthen cold chain systems. Solar direct-drive refrigeration, real-time temperature monitoring, electronic logistics management information systems, and drone-enabled last-mile delivery have improved reliability, visibility and access in selected contexts. However, many innovations remain pilot-based, donor dependent and insufficiently integrated into national systems.

These findings highlight that strengthening vaccine cold chain systems in developing countries requires a systems-based approach. Sustainable improvement depends not only on technological innovation but also on coordinated investments in governance, financing, workforce capacity, maintenance and data integration.