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US begins rollout of Johnson & Johnson coronavirus vaccine

The pharmaceutical company will ship close to 4 million doses Monday.

"For the last 13 months our physicians, our scientists, our engineers have been working around the clock to make this day possible," Alex Gorsky, CEO of Johnson & Johnson, said during an appearance on "Good Morning America" on Monday. "We couldn't be more excited."

The J&J vaccine does not use the mRNA technology used in the other two approved vaccines, which teach cells to make a protein that prompts an immune response.

Instead, the J&J vaccine uses a viral vector method where a different virus is introduced as a bit of coronavirus’ genetic material into the cells. The body's immune system then learns to identify and overcome the coronavirus.

The J&J vaccine can be stored in normal refrigerators while the Pfizer and Moderna vaccines need to be stored at below-freezing temperatures.

In its trials, the pharmaceutical company said its vaccine was 85% effective at preventing severe illness and 100% effective at preventing hospitalizations and deaths 28 days after individuals were vaccinated.

"It's important to remember about the Johnson & Johnson vaccine is we did the clinical trials roughly from October 2020 to January of this year and it was really during the peak of the incidence rate of this virus," Gorsky said.

The vaccine was tested in countries known to have potentially more dangerous variants, including Brazil and South Africa. The data found the vaccine worked against all known variants at preventing severe disease.

The J&J doses will be administered based on the eligibility requirements of each state.

Officials at the White House told ABC News they project 20 million doses will be delivered by the end of the month, but it’s not clear when exactly those doses will arrive.

“We do not expect any additional deliveries next week, and we expect deliveries to be uneven during the weeks of March,” the official said. .As of Sunday, the U.S. has delivered nearly 96.5 million coronavirus vaccine doses and administered 75.2 million doses, according to the U.S. Centers for Disease Control and Prevention. About 24.8 million Americans, roughly 7.5% of the U.S. population, have had two doses of the mRNA vaccines, according to the CDC.

"When I say 100 million in the first half of the year that's 100 million shots in arms for Americans and even more for people around the world so this will be an important addition for health care systems and patients and consumers around the world," Gorsky said.

ABC News' Anne Flaherty and Stephanie Ebbs contributed to this report.