The world's largest COVID-19 vaccine trial has officially started.
The Associated Press reports the first of about 30,000 volunteers received a trial dose Monday. The experimental vaccine was developed by the National Institutes of Health and biotechnology company Moderna.
Unlike most vaccines, which introduce a small amount of a virus into a patient's system, Moderna's vaccine carries genetic material called mRNA. That mRNA is supposed to trigger an immune response in the body.
In order to test whether the vaccine really protects against the coronavirus, trial participants will receive either a shot of the real vaccine or a placebo.
Trial participant: "Either way, it's a really important role to have, to be a part of that research. And I never thought that I'd do something like this."
Researchers will track the volunteers after they receive two injections to see if one group experiences more COVID-19 infections than the other.
Moderna has previously said it's on track to manufacture as many as 1 billion doses of the vaccine starting in 2021. It says people who receive two doses of the vaccine could be protected from the coronavirus for up to two years.
Additional reporting from Lauren Neergaard of the Associated Press. Contains footage from CNN.