however, these problems are not really problems because a new drug emerges, with short-term research that suggests it is a better drug after all. 이게 앞문장이구요.

that is , until new research confirms that it is neither as effective nor as safe as previously thought.

여기서 that is 는 즉, 다시말해서 같고.. 주절이 생략된것 같은데 의미는 대충 감이 오는데

정확하게 주절이 어떻게 생략된걸까요.