A top spokesman in the U.S. Department of Health and Human Services abruptly resigned over reports of internal clashing over management and escalating health emergencies.

Kennedy's acknowledgement of the value of the measles vaccine comes as the outbreak that began in Texas continues to grow. So far, nearly 150 cases and one death—the first U.S. fatality from the disease in more than 10 years—have been confirmed. It's the largest measles outbreak in the U.S. in decades.