Democratic presidential nominee Joe Biden met with researchers and scientists to discuss how he would manage the pandemic, as polling shows a majority of Americans don’t trust President Trump on the coronavirus vaccine.

On the same day as the Trump administration released its guidelines for distributing a coronavirus vaccine, Democratic presidential nominee Joe Biden pushed back on the guidance, saying the administration hasn’t “put [a plan] in place for real yet,” and there isn’t enough detail in what was released.

“Let me be clear: I trust vaccines. I trust scientists. But I don’t trust Donald Trump, and at this moment the American people can’t either,” Biden said, speaking from Wilmington, Delaware. Biden’s comments echo recent polling that shows that a majority of Americans don’t trust what President Trump says about a potential vaccine.

Before his press conference, Biden met with public health experts and scientists about the proper way to finish testing and distribute any potentially effective coronavirus vaccine. He opened by highlighting Trump’s remarks last night at an ABC News town hall.

“Incredibly, Donald Trump insists he wouldn’t have done anything differently—not one thing,” Biden said. He talked about the Trump administration’s indifference on universal mask guidelines and the difficulties that frontline workers have had securing personal protective equipment.

“We can’t repeat those fiascos when it comes to a vaccine,” Biden said. “The stakes are too high.” The Democratic nominee added that he expects that a vaccine for most Americans won’t be available “well into 2021.”

Biden’s comments echoed testimony by Centers for Disease Control and Prevention (CDC) Director Robert Redfield, who told a Senate committee earlier Wednesday that he estimated a vaccine in 2020 would be available in a “very limited supply.” Redfield indicated that the vaccine wouldn’t be broadly available until the summer of 2021.

The CDC director’s comments also contradict Trump’s assertions at Tuesday night’s town hall, when he said a vaccine could be three to four weeks away. White House Press Secretary Kayleigh McEnany also echoed the president’s timeline at the White House on Wednesday, but lengthened it: “We do believe that it will be widely available by the end of the year.”

During his testimony, Redfield also said that masks could help more than a vaccine, depending on the efficacy of the vaccines that become available.

“I might even go so far as to say that this face mask is more guaranteed to protect me against COVID than when I take a COVID vaccine,” Redfield told the Senate panel, holding his mask.

At his press conference, Biden outlined how he would approach a universal mask mandate in the United States.

“I would call all of the governors to the White House,” Biden said, “I would make the case why it’s necessary, I’d have the scientists lay out in detail why … we have to have this national mandate.”

In contrast, Trump has refused to enact a national mask mandate, and last night questioned their effectiveness, mentioning that waiters don’t like wearing them. He also blamed Biden for not enacting a national mask mandate, despite Trump’s own current occupancy of the White House.

“I’m not the president, he’s the president,” Biden said. “I mean, c’mon.”