WASHINGTON (NewsNation Now) — The White House coronavirus response team assembled by President Joe Biden addressed the public Monday, as the rapid rollout of the nation’s third approved COVID-19 vaccine gets underway.

The top U.S. infectious diseases expert Dr. Anthony Fauci, Centers for Disease Control and Prevention Director Dr. Rochelle Walensky, and other members of the team held a briefing, starting at 11 a.m. EST. The entire press conference is provided in the player above.

White House COVID-19 response coordinator Jeff Zients said on Monday that scheduling coronavirus vaccination appointments remains too difficult in many places.

Meanwhile, Walensky put attention on the lifting of coronavirus restrictions around the country, saying she was “really worried” about rolling back measures to contain the pandemic.

“Please hear me clearly: At this level of cases, with variants spreading, we stand to completely lose the hard-earned ground we have gained. These variants are a very real threat to our people and our progress,” she said. “Now is not the time to relax the critical safeguards that we know can stop the spread of COVID-19 in our communities, not when we are so close.”

The briefing comes as nearly 4 million doses of the newly approved Johnson & Johnson vaccine are being shipped out to states.

The drugmaker’s top executive, Alex Gorsky, said Monday that Americans should be able to get the single-dose shot within the next 24 to 48 hours.

The White House has said that the entire stockpile of the newly approved single-dose Johnson & Johnson vaccine will go 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.

Though the new shot is easier to administer and requires only one dose, the administration is not altering its distribution plans.

Dr. Fauci urged Americans on Sunday to accept any of the three vaccines that becomes available to them first.

“All three of them are really quite good, and people should take the one that’s most available to them. If you go to a place and you have J&J, and that’s the one that’s available now, I would take it,” Fauci said on NBC’s “Meet the Press.”

The U.S. government authorized Johnson & Johnson’s single-dose COVID-19 vaccine on Saturday, making it the third to be available in the country following ones from Pfizer/BioNTech and Moderna. Both of those vaccines require two doses and need to be shipped frozen. The J&J vaccine can be shipped and stored at normal refrigerator temperatures.

Biden has said there should be enough supply to vaccinate all Americans by the end of July.

More than 96.4 million vaccine doses have been distributed in the United States with more than 75 million doses administered, according to the CDC.

The Associated Press and Reuters contributed to this report.