The producers of “Happiness” teased, “Everyone’s daily lives will become completely different due to an unidentified new infectious disease. The struggle for survival during an extreme crisis that is eroded by anxiety and fear will be depicted realistically. The current ongoing fear of what can actually happen during an ‘infectious disease’ and the psychological warfare in an enclosed space will deliver a different kind of fun as well as genre-based pleasure.” https://www.soompi.com/article/1492297wpp/park-hyung-sik-han-hyo-joo-and-jo-woo-jin-witness-the-world-falling-apart-in-poster-for-upcoming-drama
The Budget of this drama is 13 billion won (~US$11.089 million) (Wikipedia).
The filming itself was a pre-production work that was all completed in 2019, but the OCN formation was confirmed only in 2021 while it was difficult to organize.
(https://namu.wiki/w/키마이라(드라마))
(https://news.nate.com/view/20210927n22141)
There was also sexual harassment allegations because of that filming was halted 1 month
(https://www.mk.co.kr/star/hot-issues/view/2019/07/522845/)
(https://entertain.v.daum.net/v/20190716205027935)
https://youtu.be/mLn62biTkSk
https://youtu.be/Yq6wQkgqYas
https://www.soompi.com/article/1492297wpp/park-hyung-sik-han-hyo-joo-and-jo-woo-jin-witness-the-world-falling-apart-in-poster-for-upcoming-drama