(CNN) — President Joe Biden on Tuesday announced that the federal government is doubling the US’ order for Pfizer’s Covid-19 antiviral pill, Paxlovid, which has been shown to reduce hospitalizations and severe illness significantly.

“Production is in full swing. The United States has more pills than any other country in the world and our supply is going to ramp up over the coming months, as more of these pills are manufactured,” Biden said during remarks at the White House. “Today I’m directing my team to work with Pfizer to double our order from 10 million to 20 million treatment courses to be delivered in the months ahead.”

Biden had announced a purchase of 10 million courses late last year.

The President also cautioned during his remarks that “we may need even more. That’s the estimate we need right now.”

The first batch of the pills, he said, were shipped out on Christmas Eve “and more will be shipped this week.”

Albert Bourla, the chairman and CEO of Pfizer, tweeted Tuesday afternoon that “by the end of September, 20M (Paxlovid) treatment courses will be delivered, with approximately 10M accelerated for delivery by the end of June.”

The announcement comes as the US reached more than 100,000 hospitalizations due to to the illness for the first time in four months.

The Omicron variant caused 95.4% of new Covid-19 cases in the US last week — significantly higher than the previous week, according to estimates posted Tuesday by the US Centers for Disease Control and Prevention.

Biden and his team have yet to disclose comprehensive details about a critical portion of a plan announced last month to tackle Covid-19 this winter — an initiative to distribute half a billion tests for free using a website.

On Tuesday, the President acknowledged that the continued shortage of Covid-19 testing “remains frustrating.”

“Believe me. It’s frustrating to me. But we’re making improvements. In the last two weeks, we’ve stood up federal testing sites all over the country. We’re adding more each and every day,” Biden said. “With more capacity for in-person tests, we should see waiting lines shorten and more appointments freed up.”

The administration is still in the procurement process, an official said. Health experts have warned the nationwide shortage of rapid at-home tests is coming during a critical period for testing as the Omicron variant disrupts daily life.

The CDC, meanwhile, is expected to update its guidance on the recommended isolation period, according to a source familiar with the plan, after the agency faced pressure to include a testing component in its new shortened isolation period.

Earlier Tuesday, the CDC also backed two major US Food and Drug Administration decisions.

The CDC announced its support of the FDA’s recommendation to shorten the time needed between completing an initial series of the Pfizer/BioNTech Covid-19 and a booster shot from six months to five months, as well as its call to authorize a third dose of the primary vaccine series for some immunocompromised children ages 5 to 11.

In the same announcement Monday, the FDA also authorized expanding booster eligibility to adolescents ages 12 to 15.

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