A cluster randomized controlled trial in 150 communities in Sierra Leone showed that last-mile delivery of vaccines and health professionals increased immunization rates by 26 percentage points within 48–72 hours. The intervention, which included community mobilization and mobile vaccination teams, also increased the number of people vaccinated by more than doubling the number of inoculations administered. The cost per person vaccinated was approximately $33, with transportation to remote villages accounting for a large share of the total cost. The study highlights the importance of addressing access barriers in low-income countries to improve vaccine uptake and equity. The results suggest that prioritizing mobile services can generate increased returns in terms of health service uptake. The study also found that low vaccination rates are related to deficiencies in access, and that cost-effective interventions can overcome these deficiencies. The findings have broader implications for global public health, as they demonstrate that mobile delivery concepts can be effective in increasing vaccination rates and reducing child mortality in remote areas. The study also emphasizes the need for international support to facilitate experimentation and learning in low-income countries. The results show that low-income countries need to experiment with creative ideas to overcome logistical challenges, such as setting up temporary clinics and sending vaccine doses and nurses to remote locations. The study also highlights the importance of bundling multiple health interventions to reduce costs per person treated. The findings suggest that the global vaccination rate can be increased and vaccine equity improved by emphasizing access interventions. The study also shows that the cost-effectiveness of the intervention is higher than many other vaccination strategies, and that the intervention can be scaled up with the support of international partners. The study has important policy implications, as it shows that achieving vaccine equity requires effective strategies to reach rural populations. The study also highlights the importance of community engagement and the need for a reliable supply of vaccines and incentives for staff to innovate. The study has limitations, including variations in costs across villages and performance differences among teams. The study concludes that last-mile delivery of vaccines is a cost-effective and effective strategy for increasing vaccination rates in remote areas.A cluster randomized controlled trial in 150 communities in Sierra Leone showed that last-mile delivery of vaccines and health professionals increased immunization rates by 26 percentage points within 48–72 hours. The intervention, which included community mobilization and mobile vaccination teams, also increased the number of people vaccinated by more than doubling the number of inoculations administered. The cost per person vaccinated was approximately $33, with transportation to remote villages accounting for a large share of the total cost. The study highlights the importance of addressing access barriers in low-income countries to improve vaccine uptake and equity. The results suggest that prioritizing mobile services can generate increased returns in terms of health service uptake. The study also found that low vaccination rates are related to deficiencies in access, and that cost-effective interventions can overcome these deficiencies. The findings have broader implications for global public health, as they demonstrate that mobile delivery concepts can be effective in increasing vaccination rates and reducing child mortality in remote areas. The study also emphasizes the need for international support to facilitate experimentation and learning in low-income countries. The results show that low-income countries need to experiment with creative ideas to overcome logistical challenges, such as setting up temporary clinics and sending vaccine doses and nurses to remote locations. The study also highlights the importance of bundling multiple health interventions to reduce costs per person treated. The findings suggest that the global vaccination rate can be increased and vaccine equity improved by emphasizing access interventions. The study also shows that the cost-effectiveness of the intervention is higher than many other vaccination strategies, and that the intervention can be scaled up with the support of international partners. The study has important policy implications, as it shows that achieving vaccine equity requires effective strategies to reach rural populations. The study also highlights the importance of community engagement and the need for a reliable supply of vaccines and incentives for staff to innovate. The study has limitations, including variations in costs across villages and performance differences among teams. The study concludes that last-mile delivery of vaccines is a cost-effective and effective strategy for increasing vaccination rates in remote areas.