[3] In 2015, during the MERS outbreak, she was responsible for press briefings and crisis management[3] as the head of the Center for Disease Prevention of KCDC and field investigation team of central task force.

[2] In 2016 Board of Audit and Inspection ordered suspension of nine public health officials including Jeong[4] for their failure to stop the worst MERS outbreak outside of the Middle East.

[13] On her last day as KCDC Director, President Moon visited its headquarters for Jeong's appointment ceremony as the first Commissioner of KDCA which is unorthodox given that the Prime Minister usually hosts such events for vice-ministerial posts.

[15] On 15 January 2021, President Moon requested Jung and KDCA to lead Korea's COVID-19 vaccination programme in addition to ongoing virus containment in the country.

[17][18] It was later revealed that Jeong rejected President Moon's requests multiple times to ease entry restrictions for asymptomatic people coming into the country at the hike of the pandemic.