COVID-19 Vaccine Candidate Heads To Widespread Testing In U.S.

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.


A view of Moderna headquarters on May 08, 2020 in Cambridge, Massachusetts. Moderna was given FDA approval to continue to phase 2 of Coronavirus (COVID-19) vaccine trials with 600 participants.

The COVID-19 vaccine candidate made by the U.S. biotech company Moderna and developed in collaboration with the National Institutes of Health starts its final phase of testing Monday.

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.

According to a list maintained by the World Health Organization, there are four other vaccine candidates to reach Phase 3 testing: three made by Chinese entities and one by a collaboration between the University of Oxford and AstraZeneca.

The Moderna vaccine is a new kind of vaccine based on the genetic material that makes up the coronavirus. Snippets of RNA (a chemical cousin of DNA) are enclosed in a nano-capsule and injected into someone’s arm. The RNA contains instructions to make a protein found of the outer surface of the coronavirus. This protein is what stimulates the immune system to make antibodies against the virus. The idea is that if this harmless protein in the vaccine can generate those antibodies, then if the vaccinated individual is exposed to the virus, their immune system will be able to fight it off.

The Phase 3 trail will take place at 89 centers around the United States. To find out more or join the study, go to and search identifier NCT04470427, or go to

Copyright 2020 NPR. To see more, visit
Today in Houston Newsletter Signup
We're in the process of transitioning services for our Today in Houston newsletter. If you'd like to sign up now, fill out the form below and we will add you as soon as we finish the transition. **Please note** If you are already signed up for the newsletter, you do not need to sign up again. Your subscription will be migrated over.