President Joe Biden announced a major partnership Tuesday afternoon between pharmaceutical giants Merck & Co. and Johnson & Johnson to help produce J&J's newly authorized vaccine and changed the vaccine timeline, saying there would be enough for every American adult by the end of May.

"About three weeks ago, we were able to say that we'll have enough vaccine supply for adults by the end of July, and I'm pleased to announce today, as a consequence of this stepped-up process that I've ordered and just outlined, this country will have enough vaccine supply ... for every adult in America by the end of May," Biden said.

He compared the two companies collaboration to what the U.S. saw during World War II and said that Johnson & Johnson's vaccine manufacturing facilities will now begin to operate 24/7.

The president also announced Tuesday that he wants teachers and school workers to receive at least one vaccine shot "by the end of March."

While Biden can't mandate that states prioritize teachers for their vaccine supplies, Biden is challenging them to do so. To help make this happen, Biden announced that starting next week and for the month of March, his administration will be using their federal pharmacy program to prioritize the vaccination of pre-k through 12 educators, staff and child care workers.

"Now I want to be very clear. Not every educator will be able to get their appointment in the first week. But our goal is to do everything we can to help every educator receive a shot this month, the month of March," he said.

While some states, like Texas, announced they are easing their restrictions Tuesday, Biden was blunt that there is still a long road ahead.

"This fight is far from over. I told you, I would be straight up with you from the very beginning. As I said many times, things may get worse again as new variants spread and as we face setbacks," he said.

"Though we celebrate the news of a third vaccine, I urge all Americans, please, keep washing your hands. Stay socially distanced. Wear masks. Keep wearing them. Get vaccinated when it's your turn. Now is not the time to let up. I've asked the country to wear masks for my first 100 days in office. Now is not the time to let our guard down," Biden continued.

Asked when things will "get back to normal," the president said he hopes "by this time next year," but added that it depends on if people continue to be "smart."

The U.S. Food and Drug Administration approved an Emergency Use Authorization for the J&J vaccine Saturday, which triggered the shipment of 3.9 million doses of the vaccine on Monday. Of those, 800,000 are expected to go directly to pharmacies. The first shots were being administered Tuesday.

J&J had originally estimated it could ship 12 million doses at the end of February in a $1 billion contract signed with the federal government in August.

Despite the low initial availability, Johnson & Johnson CEO Alex Gorsky said the company expects 20 million doses to be available by the end of March and to meet its contractual obligation for 100 million doses by the end of June. He also said Johnson & Johnson is expected to produce almost 1 billion doses by the end of the year.

White House press secretary Jen Psaki said earlier Tuesday that the partnership "should" help Americans get the shots sooner.

"It definitely will expedite the efforts of the United States government, having enough vaccines on hand to vaccinate the American public," Psaki told ABC News Senior White House Correspondent Mary Bruce.

Merck said the U.S. government was giving it $268.8 million "to adapt and make available a number of existing manufacturing facilities" for the production of the vaccines and medicines.

J&J confirmed the arrangement.

"We will continue to invest in collaborations so we can bring our full resources and best scientific minds to combat this pandemic," Johnson & Johnson said in a statement.

The J&J vaccine on Saturday became the third FDA authorized COVID-19 vaccine, joining Pfizer and Moderna. However, those other vaccines require two doses for full immunization. The J&J vaccine is not only administered as a single dose but is also easier to store, only requiring regular refrigeration.

The J&J vaccine also differs from its competitors in that clinical trials were conducted in Latin America and South Africa and tested against different COVID-19 variants.

"About 40% of the patients in the trial were in Latin America," Gorsky said on Good Morning America on Monday. "We had about another 15% in South Africa. In South Africa over 90% of those patients were infected with the South African strain.

Gorsky said the vaccine is 100% effective against hospitalizations and deaths.

Biden administration officials are urging Americans to get vaccinated to help control the coronavirus pandemic and advising people to take any vaccine that is offered.

"All of these vaccines are safe. They are effective. They've been approved by the FDA," Psaki said on Monday.

The country's leading infectious-disease expert, Dr. Anthony Fauci, is also stressing that Americans should take whatever vaccine is provided to them, saying he would do the same.

"I'm vaccinated now," he said on ABC's "This Week." But if I were not vaccinated, and I was going to go into a clinic, and they said, 'hey, we have J&J now, or you can wait three weeks or so to get another one,' I would take the one that is available to me now, because the quicker you get vaccinated, the more quickly you will be protected, and you will add on to the overall protection in your county, in your country."

ABC News' Anne Flaherty contributed to this report