According to the global vaccine alliance Gavi, the "solar direct-drive" refrigerators, which are simple coolers that do not require fuel or batteries, have increased child vaccinations in the poorest rural provinces of DRC by 50% in the past year. This has led to a significant reduction in child mortality in DRC compared to two decades ago. Last year, over 18 million children were vaccinated against a deadly measles outbreak, which has significantly decreased in recent weeks. The world is now preparing to launch a large-scale immunisation campaign once COVID-19 vaccines are available. However, delivering millions of vaccinations in Africa, a continent with weak health systems and limited electricity, will be a challenging task. It is uncertain whether current off-grid refrigerators are capable of maintaining the necessary temperature for vaccines. Refrigeration is crucial for the distribution of vaccines, as many require temperatures between 2 and 8 degrees Celsius. However, some COVID-19 vaccine candidates may need storage as low as minus 80C. Establishing a cold chain distribution network for these vaccines will require consistent low temperatures from production facilities to airports to remote areas. Despite progress in cold storage technology, many African countries still lack sufficient cold chain networks. Toby Peters, a professor at the University of Birmingham in Britain specializing in cooling systems for food and medicine, described the global logistical challenge of ensuring proper refrigeration for vaccines as possibly the largest the world has ever faced. This challenge is particularly daunting for sub-Saharan African countries with large rural populations. In the past, outdated kerosene-powered refrigerators in health centers in the Democratic Republic of Congo often broke down, leading to vaccine damage or destruction. The introduction of first-generation solar refrigerators was an improvement, but they depended on storage batteries that often failed after a few years and were difficult to replace. However, the development of solar direct-drive refrigerators about a decade ago revolutionized vaccine storage in remote areas. These refrigerators, which cost between $3,500 and $9,000, are directly connected to solar panels, using thermal energy to create a layer of ice that keeps vaccines cool for many days regardless of the weather. In 2016, only 16% of rural health centers in the Democratic Republic of Congo had functioning refrigerators, as reported by Gavi. Today, nearly 80% have been equipped with many using direct-drive solar units. These new refrigerators have allowed for 24,000 monthly immunization sessions in the poorest provinces, a 50% increase from 2018. According to Clemmer, this has transformed vaccine delivery for children in sub-Saharan Africa. Karan Sagar, a doctor leading the health systems and immunization strengthening team at Gavi, attributes a 25% increase in child vaccination rates in Africa over the past decade to the off-grid equipment. Since 2017, Gavi has spearheaded a $250-million initiative to distribute over 15,300 solar direct-drive fridges to numerous African nations, with the Democratic Republic of Congo receiving nearly 3,400 units and Nigeria receiving 5,400 units. Last year, 87% of children in these countries were vaccinated for diphtheria, tetanus, and pertussis, showcasing the efficacy of supply chains in reaching even the most remote communities. Moving vaccines swiftly and securely from manufacturing sites to various locations in Africa will require multiple logistical steps, with solar refrigerators being just one of them. Throughout the entire process, which includes transportation by airplanes, warehouses, trucks, motorbikes, bicycles, canoes, and even drones, it is crucial to maintain specific, very cold temperatures for the vaccines, similar to other perishable goods. Additionally, a much larger quantity of vaccines will be required. While child vaccination campaigns typically target around 115 million infants globally each year, experts anticipate that the COVID-19 vaccine will need to reach up to 750 million people in Africa alone. To address this monumental task, cold chain expert Peters is spearheading a government-supported initiative to assess Africa's requirements for distributing the eventual COVID-19 vaccine, collaborating with various nonprofit, commercial, and academic partners. They are drawing from the successes of Rwanda, a country in central-east Africa that has made significant advancements in establishing efficient and environmentally-friendly cold chains for food and vaccine distribution. The system is centered around a single warehouse that acts as a cooling center for vaccines distributed to various healthcare facilities, including those in remote areas equipped with solar fridges. The World Health Organization reports that the vaccines are reaching over 95% of the population in Rwanda. However, expanding this success to other countries, such as Nigeria, will be challenging. According to Peters, countries with established commercial food cold chains will serve as a model for replication. Peters stated that they have the knowledge and ability to transport large quantities of fresh food from small farms in Africa to consumers in Europe, and they should apply this expertise to moving vaccines. However, the challenge lies in the ultra-cold storage requirements of COVID-19 vaccines, which may exceed the capabilities of solar direct-drive fridges. Rwanda and the DRC have experience with ultra-cold storage for vaccines, as seen with a new vaccine during the Ebola outbreak. These vaccines were kept at extremely low temperatures using "super thermos" coolers filled with synthetic alcohol ice, but the quantities were much smaller than what would be needed for a COVID-19 vaccine. Sagar pointed out that very few African economies have the capacity for ultra-cold chain storage. Peters is optimistic that COVID-19 vaccines will only require standard cold storage temperatures of 2-8C, which can be provided by solar direct-drive refrigerators in rural health centers. He emphasized that if vaccines require colder temperatures, it will present a significant challenge for mainstream cold chains.