The head of the Centers for Disease Control and Prevention made an impassioned plea to Americans Monday not to let their guard down in the fight against COVID-19, saying she has a recurring feeling “of impending doom,” even as President Joe Biden announced further efforts to expand access to coronavirus vaccines.

Speaking during a virtual White House briefing, Dr. Rochelle Walensky grew emotional as she reflected on her experience treating COVID-19 patients who are alone at the end of their lives.

“We have so much to look forward to, so much promise and potential of where we are and so much reason for hope,” she said. “But right now, I’m scared.”

“I’m going to lose the script, and I’m going to reflect on the recurring feeling I have of impending doom,” she said.

Cases of the virus are up about 10% over the past week from the previous week, to about 60,000 cases per day, with both hospitalizations and deaths ticking up as well, Walensky said. She warned that without immediate action the U.S. could follow European countries into another spike in cases and suffer needless deaths.

“I have to share the truth, and I have to hope and trust you will listen,” she added.

Later Monday, Biden addressed the nation from the White House, declaring, “If we let our guard down now, we can see the virus getting worse, not better. People are letting up on precautions, which is a very bad thing.”

Biden delivered a direct appeal to governors, state and local leaders to reinstate mask-wearing requirements if they have eased them.

“Please, this is not politics, reinstate the mandate if you let it down,” he said.

Biden announced that by April 19 at least 90% of the adult U.S. population would be eligible for vaccination — and would have access to a vaccination site within 5 miles of home. Quick vaccination would still depend on supply as well as overcoming some people’s hesitancy about the shots.

Biden had previously directed that all states make all adults eligible for vaccination by May 1, but many have moved to lift eligibility requirements sooner in anticipation of supply increases.

Meanwhile, the White House was moving to double the number of pharmacies participating in the federal retail pharmacy program — which has emerged as among the most efficient avenues for administering vaccines — and increase the number of doses for them to deliver. The retail pharmacies are located in close proximity to most Americans and have experience delivering vaccines like the flu shots.

Biden announced that the U.S. was expecting delivery of 33 million doses of COVID-19 vaccine this week — including 11 million doses of the single-dose Johnson & Johnson shot.

“The president has not held back in calling for governors, leaders, the American people to continue to abide by the public health guidelines,” said White House press secretary Jen Psaki. “He will continue to do that through all of his engagements.”

Walensky and Dr. Anthony Fauci, the nation’s top infectious disease expert. appealed to elected officials, community leaders and everyday Americans to maintain social distancing measures and mask wearing.

“We are doing things prematurely,” Fauci said, referring to moves to ease up on restrictions. Walensky appealed to Americans, “Just please hold on a little while longer.”

She added: “We are not powerless, we can change this trajectory of the pandemic.”

Walensky pointed to an uptick in travel and loosening virus restrictions for the increase in cases. “People want to be done with this. I, too, want to be done with this,” Walensky said.

“We’ve seen surges after every single holiday,” she reiterated: “Please limit travel to essential travel for the time being.”

The White House, meanwhile is ruling out the creation of a national “vaccine passport” for Americans to verify their immunization status, saying it is leaving it to the private sector to develop a system for people show they’ve been vaccinated. Some other countries are establishing national databases to allow vaccinated people to resume normal activities.

“We do know that there is a segment of the population that is concerned that the government will play too heavy-handed of a role in monitoring their vaccinations,” said White House COVID-19 adviser Andy Slavitt. He said officials are worried that “it would discourage people” from getting vaccinated if the federal government was involved.

The administration, instead, is developing guidelines for such passports, touching on privacy, accuracy and equity, but the White House has not said when those guidelines will be ready.