The U.S. is at the forefront of the race to vaccinate young children. Many governments elsewhere are treading more cautiously.

In Mexico, the president says he won’t be held hostage by vaccine makers and there are no plans to inoculate under-18s except those at risk. In many parts of Africa, rollouts are going so slowly that vaccinating children is a distant ambition. Some governments are waiting to see how the campaign in the U.S. goes before moving ahead.