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.

The top spokesperson at the Health and Human Services Department resigned Monday after clashing with Robert F. Kennedy Jr. over his response to the measles. Thomas Corry said he called it quits “effective immediately” in a post on his LinkedIn account just two weeks into his tenure at the agency.

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.