Leonida Lipshy, RN in the COVID unit at the Broward Health Medical Center, gives Dr. Nadav Fields, DO., internal medicine, Broward Health Imperial Point, a shot of the Moderna COVID-19 vaccine on December 23, 2020 in Fort Lauderdale, Florida. (Photo AdvertisementNew drugs, vaccines or treatments usually go through rigorous tests and evaluations before reaching regulators for approval.For vaccines, researchers compare what happens when a large group of volunteers gets the shots, versus what happens to another large group that doesn't.