The "solar direct-drive" refrigerators, which are simple coolers that do not rely on fuel or batteries, have played a significant role in increasing child vaccination rates in the poorest rural provinces of the DRC by 50% in the last year, as reported by the global vaccine alliance Gavi. This has contributed to a 50% reduction in child mortality in the DRC compared to two decades ago. Over 18 million children were vaccinated against a deadly measles outbreak last year, which has significantly slowed down in recent weeks. With the hope of launching a large-scale immunization campaign once COVID-19 vaccines are available, the world faces the challenge of delivering millions of vaccines in Africa, a continent with weak healthcare systems and limited access to electricity. It is still uncertain if current off-grid refrigerators are able to maintain the necessary low temperatures for vaccines. Refrigeration is crucial for the distribution of vaccines, as many require specific cooling temperatures ranging from 2 to 8 degrees Celsius, while some COVID-19 vaccine candidates may need storage as low as minus 80 degrees Celsius. Establishing a cold chain distribution network for COVID-19 vaccines will be challenging, as it will require consistent low temperatures from manufacturers to airports to remote rural areas. Despite advancements in cold storage technology that have saved numerous lives through vaccinations, many African countries still lack sufficient cold chain networks. Toby Peters, a professor specializing in cooling systems for food and medicine at the University of Birmingham in Britain, described the logistical challenge of providing refrigeration in sub-Saharan African countries with rural populations as one of the largest challenges the world has ever faced. In the 1990s, outdated kerosene-powered refrigerators in health centers in the DRC were causing vaccines to be damaged or destroyed. The introduction of first-generation solar refrigerators was an improvement, but they had issues with storage batteries failing after a few years. However, the development of solar direct-drive refrigerators about a decade ago has addressed these problems. These refrigerators, which cost between $3,500 and $9,000, are directly wired to solar panels, allowing thermal energy to freeze a layer of water that keeps vaccines cool for many days, regardless of the weather. In 2016, only 16% of rural health centers in the DRC had functioning refrigerators, according to Gavi. Today, nearly 80% of these centers have been equipped, many with direct-drive solar units. These improvements have led to 24,000 monthly immunization sessions in the nine poorest provinces in the past year, a 50% increase from 2018. According to Clemmer, this has greatly improved vaccine delivery for children in sub-Saharan Africa. Karan Sagar, a doctor leading the health systems and immunizations 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 countries, with the Democratic Republic of Congo receiving nearly 3,400 units and Nigeria receiving 5,400 units. According to Sagar, 87% of children in these countries received the initial dose of a vaccine for diphtheria, tetanus, and pertussis last year, showcasing the effectiveness of supply chains in reaching even the most remote areas. Moving forward, Africa will need to address not only ultra-cold storage for COVID-19 vaccines but also implement various measures to ensure swift and secure transportation of vaccines from manufacturing sites to urban and rural locations across the continent. Throughout the transportation process, including airplanes, warehouses, trucks, motorbikes, bicycles, canoes, and even drones, the vaccines must be stored at specific cold temperatures, similar to other perishable items. The COVID-19 vaccine will require substantially larger quantities than child vaccination campaigns, with experts estimating the need to reach up to 750 million people in Africa alone. To address this challenge, cold chain expert Peters is spearheading a government-supported initiative to assess Africa's requirements for distributing the COVID-19 vaccine, collaborating with various partners from nonprofit organizations, commercial entities, and academic institutions. They are leveraging insights from Rwanda, a country in central-east Africa that has made significant advancements in establishing efficient, environmentally friendly cold chains for delivering food and vaccines. The system is centered around a single warehouse that functions as a cooling center for vaccines distributed to various healthcare facilities, including district hospitals, health centers, and remote rural health posts. Many of these facilities are equipped with solar fridges. The World Health Organization reports that the vaccines are reaching over 95% of the population in Rwanda. However, duplicating this success in other countries will be challenging, especially in larger countries like Nigeria. According to Peters, a food cold chain model with larger-scale commercial capacity will be necessary. Peters explained that they have expertise in transporting fresh food from small farms in Africa to consumers in Europe, but transferring this knowledge to vaccines may be challenging due to the ultra-cooling requirements of COVID-19 vaccines. Rwanda and the DRC have experience with ultra-cold storage for vaccines, such as during the Ebola outbreak, using "super thermos" coolers with synthetic alcohol ice to maintain temperatures of minus 60-80C for up to 6.5 days. However, the quantities needed for a COVID-19 vaccine would be much larger. Sagar pointed out that very few African economies have the capability for ultra-cold chain storage. Peters is optimistic that COVID-19 vaccines will only need standard cold storage temperatures of 2-8C, which can be provided by solar direct-drive refrigerators at rural health centers. He stated that if vaccines require colder temperatures than that, it will pose a significant new challenge for mainstream cold chains.