(NPR) — A COVID-19 vaccine candidate developed by the company Moderna and the NIH begins its final phase of testing today.
It could take as many as 30,000 volunteers — and the entire process will likely take months.
A COVID-19 vaccine candidate developed by the U.S. company Moderna and the National Institutes of Health starts its final phase of testing. It's one of a handful of candidates to reach this stage.
This phase is called Phase 3 efficacy testing, and it is designed to see if the vaccine actually prevents disease. Up to 30,000 volunteers will be assigned to one of two groups. One group will receive two injections spaced approximately 28 days apart of mRNA-1273, as the vaccine is known. The other group will receive an injection containing only salt water. Neither the volunteer nor the person administering the injection will know what's in the syringe in order to avoid bias in favor of one outcome or another. Of course, people running the trial will know who is getting what.
Researchers will monitor both groups to see who, if anyone, gets sick. Organizers of the trial say there will have to only be approximately 150 cases of COVID-19 among study participants to say with confidence that the vaccine is actually preventing disease. How long it takes to reach that number, and how many participants will have to be enrolled in the study, is an open question. It depends in part on how much the virus is circulating in the communities where the trial takes place. It could take as many as 30,000 volunteers to get the answer, and the entire process will probably take months.