Yet Another Vaccine Challenge: Distributing It Around the World

In the quest to develop shots against Covid-19, researchers have overcome challenges that typically make vaccine projects stretch across years if not decades. Assuming one or more of their experimental vaccines proves safe and effective in late-stage trials — a huge feat in itself — drug companies and health officials will next face a whole new set of obstacles in their effort to deliver the shots widely around the world. Preparations for vaccinating the planet’s 7.8 billion people are already