Nearly 4 million doses of the newest COVID-19 vaccine were shipped Sunday night and will begin to be delivered to states for injections starting Tuesday.

The White House said the entire stockpile of the newly approved single-dose Johnson & Johnson vaccine went out immediately. J&J will deliver about 16 million more doses by the end of March and 100 million total by the end of June, but the distribution would be backloaded.

The FDA said J&J’s vaccine offers strong protection against what matters most: serious illness, hospitalization and death. One dose was 85% protective against the most severe COVID-19 illness, in a massive study that spanned three continents — protection that remained strong even in countries such as South Africa, where the variants of most concern are spreading.

“This is really good news,” Dr. Francis Collins, director of the National Institutes of Health, told The Associated Press during the weekend. “The most important thing we can do right now is to get as many shots in as many arms as we can.”

Though the new shot is easier to administer and requires only one dose, the administration is not altering its distribution plans. The White House is encouraging Americans to take the first dose available to them, regardless of manufacturer.

On Sunday, the Atlanta-based Centers for Disease Control and Prevention said about 49.8 million people have received at least one dose of a COVID-19 vaccine, including about 24.8 million people who have been fully vaccinated.

CDC advisers have voted overwhelmingly to recommend the new J&J vaccine for adults 18 years old and up. The ruling followed emergency authorization of the vaccine by U.S. regulators a day earlier. The same CDC panel previously recommended use of the two vaccines from Pfizer and Moderna authorized in December.

Members of the group emphasized that all three vaccines now available in the U.S. are highly protective against the worst effects of the virus, including hospitalization and death.

J&J plans to ship several million vaccine doses to states in the coming week, delivering 20 million shots by the end of March.

Last month, The New York Times called on President Joe Biden’s administration to shoot for loftier vaccination goals. Biden had previously committed to giving shots to 1 million Americans per day, a level, the Times said, Donald Trump’s administration nearly reached in its final days.

Biden has since raised the daily target to 1.5 million, but the Times said the new Democratic president should now aim for 3 million shots per day.

On Monday, FedEx Express said it has begun shipping the new vaccine on behalf of McKesson Corp. to dosing centers throughout the U.S.

“As vaccine production ramps up and more vaccines are approved, we expect to see a significant uptick in COVID-19 vaccine and supply kit volume moving through our network,” said Don Colleran, president and CEO for FedEx Express. “As manufacturers obtain approval to ship COVID-19 vaccines with greater temperature ranges and varying dosing allotments, we anticipate more of these packages moving to more places through our global network.”