The U.S. is hoping to have about 40 million doses of Covid-19 vaccine available to distribute by the end of 2020, according to Secretary of Health and Human Services Alex Azar.

"By the end of December, we expect to have about 40 million doses of these two vaccines available for distribution pending FDA authorization — enough to vaccinate about 20 million of our most vulnerable Americans," Azar said during a briefing on Wednesday.

"And production of course would continue to ramp up after that," he added.

Though the US Food and Drug Administration (FDA) must approve any vaccine, doses have already been manufactured in anticipation that one or more would get approval.

The government announcement comes in the wake of U.S. pharmaceutical company Pfizer Inc and its German partner BioNTech intending to submit their candidate vaccine for approval for emergency use in the U.S. on Friday.

The companies said their Phase 3 trial was now complete and that it revealed the vaccine was 95 percent effective at preventing symptomatic Covid-19.

The U.S., the worst-affected country in the world by the pandemic, has reported more than 11.4 million confirmed coronavirus cases and nearly 250,000 deaths, according to the Johns Hopkins University.

(With input from agencies)