As the world enters its third year fighting the COVID-19 pandemic, health care professionals have administered 10 billion-plus vaccine doses worldwide, protecting large majorities of people in rich countries. Yet few doses have reached those living in war zones or places affected by conflict or violence, who remain largely unvaccinated and vulnerable to the disease. Preventing those countries from falling further behind will require increasing the supply of vaccines, improving delivery and overcoming barriers to vaccine acceptance. It will also necessitate doing more to navigate the politics o...