In an eve-of-Thanksgiving address on Wednesday, Joe Biden drew on historic hardships and his deep personal loss to make a passionate appeal for resilience, asking Americans to endure a national holiday amid restrictions on travel and gatherings imposed to fight the pandemic.

More than 12.6m cases of Covid-19 have been recorded in the US and more than 260,000 people have died. Vaccines are imminent but hospitalisations and deaths are surging, straining infrastructure to breaking point as leaders warn of impending disaster.

His speech struck a note of unity. “We need to remember, we’re at war with the virus, not with each other,” Biden said from Wilmington, Delaware, where he is continuing transition work before his inauguration as the 46th president in Washington on 20 January.

The tone was in marked contrast to speeches by Donald Trump, who shortly after Biden spoke announced in a tweet that he was giving a full pardon to Michael Flynn, his first national security adviser who had pleaded guilty to lying to the FBI about contacts with a Russian official.

While Trump has allowed the Biden transition to proceed he has not conceded defeat or stopped making baseless claims of electoral fraud. On Wednesday the president cancelled a trip to Gettysburg meant to support efforts to overturn his defeat in Pennsylvania, after at least two aides to lawyer Rudy Giuliani tested positive for Covid-19. Trump instead addressed state Republicans remotely, claiming: “This election was lost by the Democrats. They cheated. It was a fraudulent election.”

On the national scene, such words increasingly seem like ambient noise. In Wilmington, from a podium emblazoned with “Office of the President-elect” and in front of an austere golden backdrop, Biden opened by quoting from a plaque at Gulph Mills, Pennsylvania which commemorates 18 December 1777, the first official Thanksgiving, celebrated in the midst of war with Britain.

Echoing previous speeches informed by the historian Jon Meacham, Biden said George Washington’s army marked the day “under extremely harsh conditions and deprivation.

“Lacking food, clothing, shelter, they were preparing to ride out a long, hard winter … In spite of the suffering, they showed reverence and character that was forging the soul of the nation. Faith, courage, sacrifice, service to country, service to each other and gratitude, even in the face of suffering, have long been part of what Thanksgiving means in America.”

Almost 250 years later, families across America are preparing for a holiday with loved ones distant or lost altogether. Switching from the epic to the personal, Biden remembered his own family’s first Thanksgiving without his wife, Neilia Hunter Biden, and young daughter Naomi, both killed in a car crash in 1972.

“I know this time of year can be especially difficult,” he said. “Believe me, I know. I remember that first Thanksgiving. The empty chair, silence that takes your breath away. It’s really hard to care. It’s hard to give thanks … It’s so hard to hope, to understand.

“I’ll be thinking and praying for each and every one of you this Thanksgiving.”

In a year marked by bitter partisan divide, the president-elect also saluted “simply extraordinary” turnout and said: “Let’s be thankful for democracy itself. Our democracy was tested this year, and what we learned is this. The people of America are up to the task.”

Biden is the first presidential candidate to receive more than 80m votes. But Trump was only 6m behind.

“Out of pain comes possibility. Out of frustration comes progress. Out of division, unity,” Biden said.

His words also struck a contrast with Trump’s actions. The president has won one election lawsuit in a battleground state – but lost 36. Regardless, he continues to solicit donations to benefit future political moves, including a possible White House run in 2024.

Nonetheless, in 56 days’ time Biden will replace Trump in office. He has unveiled his nominations for key foreign policy and national security posts and will reportedly name his economic team on 2 December. From Monday, he will receive the president’s daily intelligence briefing.

Democrats and Republicans in Congress are preparing for Biden to abandon Trump’s state-by-state approach to fighting the pandemic and build a national strategy instead. Democrats believe a Biden plan should include elements of the House’s $2tn coronavirus aid bill which aims to revive the US economy. Republicans have resisted big spending but agree new funding is needed.

Biden must also plan for the vaccination of hundreds of millions.

In an interview with NBC broadcast on Tuesday, he said: “The [Trump] administration has set up a roll-out [of] how they think it should occur, what will be available when and how. And we’ll look at that. And we may alter that, we may keep the exact same outline. But that’s in train now. We haven’t gotten that briefing yet.”

Last week, some lawmakers expressed anger over a lack of federal coordination with Biden. On Tuesday, health secretary Alex Azar said his department “immediately” started working with the president-elect after the General Services Administration acknowledged the election result. It did so on Monday, more than two weeks after the race was called.

Biden told NBC he thought vaccine distribution should focus “on obviously the doctors, the nurses, those people who are the first responders. I think we should also be focusing on being able to open schools as rapidly as we can. I think it can be done safely … Now, maybe, the hope is we can actually begin to distribute it, this administration can begin to distribute it before we are sworn in to take office.”

In his speech in Wilmington on Wednesday, Biden hailed “significant record-breaking progress in developing a vaccine” and said the US was “on track for the first immunisations to begin by late December, early January.

“We’ll need to put in place a distribution plan to get the entire country immunised as soon as possible, which we will do. It’s going to take time. And hopefully the news of the vaccine will serve as incentive to every American to take simple steps to get control of the virus.”

Biden listed such steps, including wearing a mask, social distancing and more.

“There’s real hope,” he said. “Tangible hope.”