The federal government will pay vaccine maker Novavax $1.6 billion to expedite the development of 100 million doses of a coronavirus vaccine by the beginning of next year, the company said Tuesday, July 7.

The deal is the largest that the Trump administration has made so far with a company as part of Operation Warp Speed, the sprawling federal effort to make coronavirus vaccines and treatments available to the American public as quickly as possible. In doing so, the government has placed a significant bet on Novavax, a company based in Maryland that has never brought a product to market.

Operation Warp Speed is a multiagency effort that seeks to carry out President Donald Trump’s pledge to make a coronavirus vaccine available by the end of the year, but the full extent of the project is still unclear. Officials have declined to list which vaccines and treatments are part of Operation Warp Speed.

In an interview Sunday, Novavax’s president and chief executive, Stanley C. Erck, initially said he was not sure where in the government the $1.6 billion was coming from. A Novavax spokeswoman later said the money was coming from a “collaboration” between the Department of Health and Human Services and the Defense Department.

In May, the administration announced it was awarding up to $1.2 billion as part of Operation Warp Speed to British drugmaker AstraZeneca, which has said that its vaccine could be available by October. Four other companies — Moderna Therapeutics, Johnson & Johnson, Merck and Sanofi — have also received federal assistance for their experimental coronavirus vaccines.

“Adding Novavax’s candidate to Operation Warp Speed’s diverse portfolio of vaccines increases the odds that we will have a safe, effective vaccine as soon as the end of this year,” Alex Azar, the health and human services secretary, said in a statement.

Erck said Novavax’s coronavirus vaccine uses the same technology as its other experimental vaccines, such as one for the flu, that have been tested in late-stage clinical trials. Novavax has recently brought in senior executives from established manufacturers like AstraZeneca and GlaxoSmithKline, he said.

“The risk they’re taking is that a company like ours — which doesn’t have a pipeline of already commercialized products — can we get to the big leagues and scale up?” he said. “And I think they’re placing the bet that we can.”

The U.S. investment comes after an international group, the Coalition for Epidemic Preparedness Innovations, awarded up to $388 million to Novavax in May to make its coronavirus vaccine available globally.

Several vaccine experts said Novavax’s vaccine would help diversify the federal portfolio by including another candidate that uses a protein-based vaccine that has worked against other pathogens, like hepatitis B. The Novavax vaccine uses microscopic particles that carry fragments of the coronavirus, prompting the body’s immune system to respond. Sanofi, which has received nearly $31 million in government funding, is also developing a vaccine that is based on viral proteins.

Other leading candidates are relying on less proven technologies. For example, Moderna is using genetic material from the coronavirus called mRNA to provoke an immune response, and AstraZeneca and Johnson & Johnson are both testing vaccines that use a harmless virus to deliver coronavirus genes into cells.

“This is a sort of diversification from other approaches, which makes a certain amount of sense,” said John P. Moore, a professor of microbiology and immunology at Weill Cornell Medical College in New York City. “You don’t want all of your eggs in one basket.”

Erck said the U.S. deal would allow Novavax to begin manufacturing the vaccines before the company concludes late-stage clinical trials, expected by the end of the year. The company would ensure that 100 million doses — enough for 50 million people to receive an initial shot and a booster — are delivered by the first quarter of 2021, if its coronavirus vaccine is proved safe and effective. In June, Novavax secured a $60 million contract from the Defense Department to guarantee the delivery of 10 million doses to vaccinate U.S. troops for the coronavirus.

Novavax began early-stage safety trials in Australia in May, and the company has said it expects to make the results available this month. It said it planned to begin so-called Phase 3 efficacy trials by the fall of this year and could release interim data by the end of 2020.

There is no vaccine for the coronavirus, and many clinical trials fail when vaccines turn out to be ineffective or to cause serious side effects. Until now, new vaccines have taken years to develop, and many experts have said the aggressive timelines set by companies and government officials for a coronavirus vaccine are overly optimistic.

Through its deal with the Coalition for Epidemic Preparedness Innovations, Novavax is also setting up manufacturing in other sites around the world, including in Europe and Asia, to serve populations outside the United States. The company is using its own facilities to scale up manufacturing and will also contract with outside companies, Erck said.

He and others have noted that more than one vaccine will need to succeed in order to vaccinate the entire world.

“Right now, we need and want everybody’s to work,” he said.