President Joe Biden on Wednesday formally announced his administration’s plans to secure an additional 100 million doses of the Johnson & Johnson coronavirus vaccine before the end of the year.

Biden made the announcement during an event with the CEOs of Johnson & Johnson and Merck, commending the rival pharmaceutical companies for joining forces to benefit the American people. Biden revealed last week that Merck is helping to produce Johnson & Johnson’s vaccine to help speed up the vaccination rate across the country.

“Today we are seeing two health companies, competitors, each with over 130 years of experience, coming together to help write a more hopeful chapter in our battle against COVID-19,” Biden said Wednesday. “What's clear is this a historic, nearly unprecedented collaboration.” 

The New York Times was the first to report the news.

Biden pledged last week that the United States will have enough doses to vaccinate every American by the end of May, and Wednesday’s announcement won’t speed up that timeline. 

It remains unclear when Johnson & Johnson will have the capacity to deliver those 100 million doses, as the company still appears to be behind on production. White House senior adviser on the COVID-19 response Andy Slavitt said earlier Wednesday that it was still too soon to lay out a specific timeline for the delivery of the Johnson & Johnson vaccines.

"This order allows for the president to plan for the future and the latter part of the year," Slavitt said during a press briefing. 

Instead, the additional doses will serve as contingency plans in the event of unforeseen circumstances. The 100 million Johnson & Johnson may be used to vaccinate children and, if necessary, serve as booster shots aimed at combating variants. They could also be shared with allies overseas after all Americans who want the vaccine are protected.

“We’re going to start off making sure Americans are taken care of first, and we’re then going to try to take care of the rest of the world,” Biden said to shouted questions on Wednesday.

Biden added that he ordered the additional 100 million Johnson & Johnson doses because, “there’s always a chance we’ll encounter unexpected challenges … a lot can happen, a lot can change, and we need to be prepared.” 

Still, the president expressed his optimism that the country is set to turn the corner on the fight against coronavirus, saying he plans to announce the "next phase" of his administration's COVID response during his primetime address on Thursday evening. 

Biden plans to “talk about what we’ve been through as a nation this past year,” he said, adding: “But more importantly, I’m going to talk a little about what comes next.”

The Food and Drug Administration last month authorized the Johnson & Johnson vaccine for emergency use, making it the third COVID-19 vaccine available in the U.S. Unlike the two-shot vaccines developed by Pfizer and Moderna, the Johnson & Johnson vaccine requires only one dose.

The Moderna and J&J vaccines are approved for people age 18 or older, while the Pfizer vaccine is authorized for 16 and up. Clinical vaccine trials are now underway for children.