WASHINGTON — The long-awaited, one-dose Johnson & Johnson COVID-19 vaccine has now been administered in the United States for the first time outside of a clinical trial.

Barbara Schmalenberger, 86, was the first to receive the vaccine at the Schottenstein Center, in Columbus, Ohio, an arena where mass vaccines are taking place, just days after it was authorized.

"It was really exciting," Schmalenberger told CNN after getting the shot. "When I got out of my car, I was shaking I was so excited. I couldn't wait."

Johnson & Johnson's is the third COVID-19 vaccine to be authorized for use in the United States. Unlike the other two, it only requires one shot and is more easily transported and stored, since it can be kept at normal refrigerator temperatures.

Almost 4 million doses of the Johnson & Johnson vaccine will be available immediately, adding to the amount allotted to states and the Federal Retail Pharmacy Program.

Schmalenberger's journey has been emotional, she said.

"I called yesterday and I was on the phone with them a long time. I was crying because I was upset, because I couldn't find out when I could get this shot and I wanted this shot. I didn't want to settle for anything else."

Almost 16 percent of the total US population has gotten at least one shot of a vaccine as of Tuesday morning, according to CDC data.