Millions of doses of America’s latest weapon against the Covid-19 coronavirus — the new, single-dose Johnson & Johnson vaccine — are already on their way to vaccination sites around the country.

The J&J vaccine was approved on Saturday — the third vaccine given a thumbs-up by Food and Drug Administration (FDA) — and by late Sunday, preparations were well under way to load trucks and cargo planes with some 4 million doses. The vaccine will be handed over to the federal government for final distribution around the country.

The first shots are expected to be given on Tuesday.

The vaccine was found to be 66-72% effective at preventing Covid-19 effective overall, but “85% effective in preventing severe disease and 100% effective in preventing hospitalization and death,” reports U.S. News. “The vaccine was also tested in clinical trials where participants were infected with new variants of the virus.”

J&J CEO Alex Gorsky spent Monday morning making the rounds of TV talk shows, trumpeting the company’s vaccine and the speed at which it was developed.

“This is the culmination of more than a year of day and night efforts on the part of our physicians, our scientists and our engineers to have a safe effective single shot, common refrigeration vaccine available for patients here but for people around the world,” Gorsky said on NBC’s Today show.

Unlike the previously approved vaccines from Pfizer and Moderna, the J&J vaccine requires only one shot, and it can be stored in standard refrigerators instead of deep freezers.

By the end of June, Gorsky said, he’s “absolutely” confident that “100 million people .. can have one shot and be done.”

Achieving that 100 million doses figure “will be crucial in meeting the Biden administration’s goal of vaccinating 300 million Americans by the end of July,” reports Axios.

“So far, only 7.5% of Americans have received both doses of the other approved vaccines,” CBS News reports, citing data from the Centers for Disease Control (CDC).

Gorksy said he’s confident that J&J can distribute 1 billion doses by the end of the year. That’s more than three times the size of the U.S. population, so if his projection is correct, the new vaccine’s impact will rapidly reach around the globe.

The Johns Hopkins Covid-19 Tracking Dashboard reported that as of Monday morning, there had been well over 28.5 million (28,609,645) positive tests for Covid in the U.S. More than half a million (513,112) Americans have died.