The Trump administration has reached a deal with Moderna Inc. to manufacture and deliver 100 million doses of the company’s Covid-19 vaccine once it is approved, according to a news release from the US Health and Human Services Department.

President Trump announced the deal during a media briefing on Tuesday.

Moderna is one of several companies manufacturing the vaccine “at risk,” as the industry calls it, meaning the company is currently making the vaccine before it is approved. Clinical trials are currently underway to test whether it’s safe and effective.

Under this contract, worth up to $1.525 billion for 100 million doses, the doses would be owned by the US government and would be distributed and used as part of its Covid-19 vaccine campaign. If the doses are used, they would be provided to Americans at no cost. The government can also acquire up to an additional 400 million doses of this vaccine, HHS said.

The vaccine, called mRNA-1273, was developed by Moderna in collaboration with the US government. It had development help from the National Institute of Allergy and Infectious Disease, and the US Biomedical Advance Research and Development Authority, known as BARDA, supported late stage clinical trials and has helped scale up manufacturing. Moderna’s advanced stage clinical trial, which started July 27, is the first government-funded Phase 3 clinical trial for a Covid-19 vaccine in the United States.

This contract is a part of the US government’s Operation Warp Speed, the federal push to get vaccines and therapeutics to market as soon as safely possible. HHS said the goal is to get effective vaccines to the American people by the end of the year.

The government has also reached a deal with Pfizer in July to produce 100 million doses of its vaccine. In August it reached a similar deal for 100 million doses with Janssen, the Johnson & Johnson vaccine arm, for its vaccine candidate. It has other deals with GlaxoSmithKline, Sanofi Pasteur, Novavax and AstraZeneca.

There are 28 Covid-19 vaccines in human trials, according to the World Health Organization.

“In creating a vaccine portfolio for Operation Warp Speed, the Trump Administration is increasing the likelihood that the United States will have at least one safe, effective vaccine by 2021,” HHS Secretary Alex Azar said in Tuesday’s news release. “Today’s investment represents the next step in supporting this vaccine candidate all the way from early development by Moderna and the National Institutes of Health, through clinical trials, and now large-scale manufacturing, with the potential to bring hundreds of millions of safe and effective doses to the American people.”