Moderna (NASDAQ:MRNA) has now moved into late-stage testing on healthcare workers. CureVac (NASDAQ:CVAC), like BioNTech a clinical-stage biotech based in Europe, announced Monday that its CvnCoV is about to enter phase 3 clinical trials, in testing that involves healthcare workers. The first participant in the study is to be administered the initial shot of the vaccine candidate on Tuesday. Image source: Getty Images. This crucial phase of testing will take place at the University Medical Center Mainz in Germany. It's a randomized, placebo-controlled study with over 2,500 individuals aged 18 and older. CureVac said it compliments the company's phase 2b/3 trial, which involved more than 35,000 people and began last week.