US President-elect Joe Biden reiterated the importance of people taking necessary steps to help prevent the spread of the coronavirus on Tuesday, saying the "darkest times" have yet to come.

He also highlighted the need for people to get vaccinated as quickly as possible, but insisted they must continue wearing masks and socially distance.

"One thing I promise you about my leadership during this crisis, I'm going to tell it to you straight. I'm going to tell you the truth," Biden told a press conference in his hometown of Wilmington, Delaware.

"And here's the simple truth -- our darkest days in the battle against COVID are ahead of us, not behind us," he added, noting more than 320,000 Americans have perished from the infectious virus.Biden's remarks came a day after he publicly received the first of his two COVID-19 vaccine shots to help "instill some confidence in the vaccine."

He again expressed his "absolute confidence in the vaccine," but noted it will take a long time to get all Americans inoculated.

"Taking the vaccine from a vial into the arm of millions of Americans is one of the biggest operational challenges the United States has ever faced for 300 million people," Biden told the press conference, adding "tens of thousands more lives" may be lost in the months to come.

"And the vaccine won't be able to stop that. So we'll still have to remain vigilant. We need everyone to mask up, stay socially distance, avoid large gatherings, particularly inside," he said.

Biden also welcomed the $892 billion economic stimulus package passed by Congress the previous day, saying it will provide temporary relief to workers and families in need.

He said he will ask the Congress to again provide such support next year.

"This bill is just a first step, a down payment in addressing the crisis or crises -- more than one that we are in. There (is) a lot more work to do," said Biden.

"Congress did its job this week, and I can and I must ask them to do it again next year," he added.

Biden is set to be inaugurated on Jan. 20. (Yonhap)