Dr. Kadlec spent 26 years as a career officer and physician in the United States Air Force. He was awarded the Bronze Star Medal for service in Iraq. In the White House Homeland Security Council, Kadlec was Director for Biodefense and Special Assistant to President George W. Bush for Biodefense Policy from 2007 to 2009.

Kadlec was Deputy Staff Director for the United States Senate Select Committee on Intelligence when he was nominated by President Donald Trump to become Assistant Secretary for Preparedness and Response (ASPR), an office within Health and Human Services. Kadlec was confirmed for this position by the United States Senate on August 3, 2017 and served there until January 2021. He is responsible for the creation of the COVID-19 vaccine development program Operation Warp Speed.