Health Secretary Robert F. Kennedy Jr. has claimed at his first congressional hearing in months that, under his leadership, the U.S. has limited the spread of measles better than any other country in the world. Measles is spreading around the world and some countries have much larger outbreaks. But experts say the U.S. is getting worse, not better, at protecting people against the spread of measles, because vaccination rates have been falling. They say Kennedy's mixed messages on vaccine safety have undermined efforts to reverse that trend.

Babies too young to be vaccinated are among the most vulnerable in measles outbreaks like the one in South Carolina, which is the largest the U.S. has seen in decades. Babies lack protection against the disease and are more likely to suffer severe complications or die. They completely depend on herd immunity, which requires nearly everyone to be vaccinated. But dropping vaccination rates have eroded protection in South Carolina and across the nation. Increasingly, some policymakers and officials push a view of vaccination as an issue of individual freedom, rather than one of public health. South Carolina’s outbreak, totaling about 1,000 cases, has slowed. But measles is spreading in many states, and the U.S. on the verge of losing its status as a country that has eliminated measles.