The "solar direct-drive" refrigerators, which are simple coolers that do not need fuel or batteries, have increased child vaccinations in the poorest rural areas of the Democratic Republic of Congo by 50% in the last year, according to Gavi. This has reduced child mortality in the DRC by half from two decades ago. Over 18 million children were vaccinated last year for a measles outbreak, which has slowed significantly recently. The global community is now preparing for a large-scale immunisation effort once COVID-19 vaccines are available. Providing millions of vaccinations in Africa, a vast continent with weak health systems and limited access to electricity, will be a challenging task. It is uncertain if current off-grid refrigerators can maintain the necessary low temperatures for vaccines. Refrigeration is crucial for the distribution of vaccines, with many requiring temperatures between 2 and 8 degrees Celsius. However, some COVID-19 vaccine candidates may need storage as low as minus 80C. A cold chain distribution network for these vaccines will need to maintain consistently low temperatures from manufacturers to rural villages. Despite progress in keeping vaccinations cold, many African countries still have significant gaps in their distribution 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 for vaccines in sub-Saharan African countries with rural populations as one of the largest challenges the world has ever faced. When Dr. William Clemmer of IMA World Health arrived in the Democratic Republic of the Congo in the 1990s, he found that many health centers were using outdated kerosene-powered refrigerators that frequently broke down, causing damage to vaccines. The introduction of first-generation solar refrigerators was an improvement, but they relied 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 refrigeration, as they are directly wired to solar panels and use thermal energy to keep vaccines cool for many days, regardless of the weather, without the need for batteries. These refrigerators cost between $3,500 and $9,000. According to Gavi, in 2016, only 16% of rural health centres in the DRC had functional refrigerators. Today, nearly 80% of these centres have been equipped, many with direct-drive solar units. This has led to a significant increase in immunisation sessions, with 24,000 sessions being conducted monthly in the poorest provinces, a 50% increase from 2018. Clemmer stated that this has revolutionized vaccine delivery for children in sub-Saharan Africa. Karan Sagar, a doctor 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 36 African countries, with the DRC receiving 3,400 units and Nigeria receiving 5,400 units. Sagar noted that 87% of children in these countries were vaccinated against diphtheria, tetanus, and pertussis last year, demonstrating the effectiveness of supply chains in reaching even the most remote areas. Moving vaccines from manufacturing sites to various destinations in Africa will require multiple steps, with solar refrigerators being just one piece of the puzzle. On every leg of the journey - from airplanes and warehouses to trucks, motorbikes, bicycles, canoes, and drones - the COVID-19 vaccine must be stored at specific, very cold temperatures, similar to other perishable goods. Health experts anticipate that substantially larger quantities of the vaccine will be required compared to regular child vaccination campaigns, with up to 750 million people in Africa alone needing to be vaccinated. 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 nonprofit organizations, commercial entities, and academic institutions. They are leveraging insights from Rwanda, a country in central-east Africa that has made significant strides in establishing efficient, environmentally friendly cold chains for food and vaccine transportation. 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 using solar fridges. The World Health Organization reports that over 95% of the population is receiving vaccines. However, duplicating Rwanda's success will be challenging, especially in larger countries like Nigeria. It will require a model similar to food cold chains with established commercial capacity. Peters stated that they have the expertise to transport fresh food from small farms in Africa to consumers in Europe and they aim to apply this knowledge to vaccines. However, the challenge lies in the ultra-cold storage requirements of COVID-19 vaccines, which solar direct-drive fridges are not designed to handle. Rwanda and the DRC have experience with vaccines that require ultra-cold storage, such as the Ebola vaccine used during the recent outbreak. These vaccines were kept at very low temperatures using "super thermos" coolers filled with synthetic alcohol ice. Despite this success, the quantities needed for an effective COVID-19 vaccine would be much larger. Sagar pointed out that very few African economies have the necessary infrastructure for ultra-cold 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. However, he acknowledges that if vaccines need to be stored at even lower temperatures, it will present a significant new obstacle.