Vaccine cold chain and understanding what underpins vaccine security for vaccine preventable diseases.

Vaccines have saved an estimated 154 million lives in the past 50 years and support 15 of the 17 United Nations sustainable development goals. Vaccines are also an important tool in the control of new outbreaks of infectious diseases. The vaccine cold chain, however, is key in enabling and empowering implementation of vaccine policy and societal protection from all vaccine preventable diseases, and is especially relevant in low and middle income countries in sub-Saharan Africa. The vaccine cold chain is a complex, highly specialised, temperature controlled supply chain network that extends from the point of vaccine manufacture to dose administration, and has multiple points of vulnerability. Large quantities of vaccines are lost because of excess heat or accidental freezing, resulting in missed opportunities for vaccination. Disruption to the provision of routine vaccines during the covid-19 pandemic resulted in millions of children not being vaccinated. The vaccine cold chain needs strategic prioritisation for investment and innovation so that the next generation of vaccine cold chains for low and middle income countries can be designed towards providing reliable and sustainable vaccine security in an uncertain world of climate change, managing the advent of new vaccine technologies, and narrowing inequalities in global health for resource poor communities. This review focuses on the vaccine cold chain in African low and middle income countries, and how new and emerging advances in vaccine science and challenges will affect the readiness to control the burden of vaccine preventable disease on the continent.