WASHINGTON (AP) — President Donald Trump on Friday hailed developments in the race for a vaccine for the resurgent coronavirus as he delivered his first public remarks since his defeat by President-elect Joe Biden, even as he refuses to concede the election.

Trump spoke from the the Rose Garden as the nation sets records for confirmed cases of COVID-19, and as hospitalizations near critical levels and fatalities climb to the highest levels since the spring. He said a vaccine would ship in “a matter of weeks" to vulnerable populations, though the Food and Drug Administration has not yet been asked to grant the necessary emergency approvals. In addition, there’s no information yet as to whether the vaccine worked in vulnerable populations or only in younger, healthier study volunteers.

Public health experts worry that Trump’s refusal to take aggressive action on the pandemic or to coordinate with the Biden team during the final two months of his presidency will only worsen the effects of the virus and hinder the nation’s ability to swiftly distribute a vaccine next year.

As states impose new restrictions in the face of rising caseloads, Trump asked all Americans to remain “vigilant." But he ruled out a nationwide “lockdown" and appeared to acknowledge that the decision won't be his much longer.

“This administration will not be going to a lockdown,” he said. “Hopefully whatever happens in the future, who knows, which administration it will be I guess time will tell, but I can tell you this administration will not go to a lockdown.”

Biden, for his part, has not endorsed a nationwide shutdown, but he appealed for Trump to take “urgent action” to curtail the spread of the virus. “The crisis does not respect dates on the calendar, it is accelerating right now,” he said in a statement Friday.

Meanwhile, Trump’s campaign prediction that the U.S. was “rounding the turn” on the pandemic has met a harsh reality, with his own White House becoming the focus of yet another outbreak.

Trump’s aggressive travel despite the virus has taken its toll on his protectors as well. The U.S. Secret Service is experiencing a significant number of cases, many believed to be linked to his rallies in the closing days of the campaign, according to one official.

White House press secretary Kayleigh McEnany, meanwhile, said Trump is “not even at that point yet” when it comes to conceding to Biden. Trump has leveled baseless allegations of widespread voter fraud, even as his own administration has said there is no evidence to support the claims. His aides suggest he is merely trying to keep his base of supporters on his side in defeat.

Trump spoke with conservative media on Friday, including Fox News' Geraldo Rivera, suggesting he would acknowledge the loss only after exhausting his legal options.

“You know, he told me he was a realist," Rivera said. “He told me he would do the right thing.”

With more than 100,000 new confirmed U.S. cases reported daily for more than a week, Trump has been more focused on tracking the rollout of a vaccine, which won’t be widely available for months. He has fumed that Pfizer intentionally withheld an announcement about progress on its vaccine trial until after Election Day, according to a White House official who was not authorized to publicly comment and spoke on condition of anonymity. Pfizer said it did not purposely withhold trial results.

Dr. Moncef Slaoui, head of Operation Warp Speed, the effort to get a vaccine to market as speedily and safely as possible, vouched for the safety of the vaccines in development. “While we are not there yet, we are close to the objective” to having a vaccine ready for deployment by the end of the year, he said.

Trump, aiming to settle political scores, said he would not ship vaccines to hard-hit New York until Democratic Gov. Andrew Cuomo signs off, noting that the state has promised to do its own review to ensure their safety. “The governor will let us know when he’s ready," Trump said.

The president has consistently played down the pandemic, which has killed more than 240,000 Americans and infected more than 10 million people in the U.S.

Trump hasn’t answered questions since before Election Day. That hasn’t slowed his Twitter habit, but he’s used it almost exclusively in recent days to rage over the election results and spread unsubstantiated allegations of voter fraud.

White House chief of staff Mark Meadows tested positive last week after attending an election night party at the White House. Others at the party also have tested positive, including White House political director Brian Jack, former White House aide Healy Baumgardner and Trump campaign advisers David Bossie and Corey Lewandowski. Lewandowski said Thursday that he believes he contracted the virus in Philadelphia while assisting the president’s election challenge there.

Biden, for his part, largely framed the election as a referendum on Trump’s handling of the pandemic. He has made addressing the virus his top priority as he moves forward with his transition. He spoke by phone Thursday with House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer about the intensifying pandemic and prospects for passage of a COVID-19 relief bill in the lame duck session of Congress.

Incoming White House chief of staff Ron Klain said Biden will appoint a “COVID coordinator” who will lead the administration’s pandemic response. Klain, speaking on MSNBC Thursday night, said the individual will have “direct access” to the president and will brief him daily on the pandemic. A team of people underneath the coordinator will supervise vaccine distribution, address supply chain disruptions and improve access to testing.

Lawrence Gostin, a public health expert at Georgetown University’s law school, said Biden will only be able to “scratch the surface” of tackling a pandemic that could be a “raging forest fire” by the time he takes office on Jan. 20.

He added that even the good news on Pfizer’s development of a vaccine that showed 90% efficacy in early trial results could be diminished if Trump doesn’t begin coordination efforts with Biden’s team on how to roll out the vaccine. Some public health experts believe the task of persuading Americans to take the vaccine and widely distributing it could be as complicated as the vaccine's development.

“I fear the next three months ahead could be the worst we’ve faced during the pandemic,” Gostin said. “America is like a ship at storm, and the captain has decided to go play golf.”

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Madhani reported from Chicago. Associated Press writers Jill Colvin and Alexandra Jaffe contributed to this report.