The leader of the White House’s effort to develop a coronavirus vaccine has predicted that by the end of January, there will be a “significant decrease” in deaths among the nation’s elderly, as high-risk populations in the United States receive vaccinations.

Moncef Slaoui, chief science adviser to Operation Warp Speed, said he expects independent advisers to the Food and Drug Administration to recommend emergency authorization for the vaccine developed by Pfizer and German biotechnology company BioNTech when the panel meets Thursday. The FDA is expected to issue the authorization soon after that. Pfizer’s vaccine is the first in line for approval in the United States.

Biotechnology company Moderna also has filed for emergency authorization of its coronavirus vaccine.

Health and Human Services Secretary Alex Azar said that if the FDA panel recommends authorization of the Pfizer vaccine later this week, people could start to receive shots “within days.”

But assuming any coronavirus vaccine is authorized, it will take months before vaccinations have any effect on the state of the pandemic in the United States, which is facing a dire surge in cases. Daily infections and hospitalization levels are reaching new highs and deaths are climbing as experts warn that the worst days may still lie ahead. Hospitals, already slammed, could see worsening numbers in coming weeks as a result of interactions during Thanksgiving, experts warn.

A federal advisory panel recommended last week that the first coronavirus vaccine doses be given to an estimated 21 million health-care workers and 3 million residents and staff in nursing homes and other long-term care facilities.

During an interview on CBS News’s “Face the Nation,” Slaoui said vaccinations may start to have an impact on infection counts for “the most susceptible people” in January and February.

In a separate interview on CNN’s “State of the Union,” he predicted that most of the “highly susceptible population,” about 100 million people, could be covered by vaccines by the middle of March.

“I am hopeful that, by the end of the month of January, we should already see quite a significant decrease in the mortality and severe morbidity associated in the elderly population,” he said on CNN. “There are, of course, many other people, unfortunately, that have co-morbidities that live outside of care facilities, that it will take more time to immunize them.”

Slaoui also countered recent criticism from President-elect Joe Biden that the Trump administration doesn’t appear to have a detailed distribution plan for the vaccine.

He said Biden’s transition team has not yet been briefed on all plans.

“We haven’t had any meetings yet,” he said on CBS News. “I know we have a meeting this coming week, and we really look forward to it because actually things have been really very appropriately planned.”

In an interview on “Fox News Sunday,” Azar called Biden’s criticism “nonsense.”

“We have comprehensive plans from the Centers for Disease Control and Prevention, working with 64 public health jurisdictions across the country,” the HHS secretary said. “We are leveraging our retail pharmacies, our hospitals, our public health departments, our community health centers. We have the McKesson-built kits that have the syringes, the diluent, the needles, the PPE needed to administer. This is being micromanaged and controlled by the United States military as well as our incredible private sector.”

Slaoui praised Biden’s plan to ask Americans to commit to wearing masks for the first 100 days after he enters the White House.

“I think it’s a good idea, it’s never too late. This pandemic is ravaging the country,” he said. “We all need to take our precaution, wear our masks, wash our hands, keep our distance, remain aware that this virus is a killer.”

Slaoui added that there is “light at the end of the tunnel, but we will not all have the vaccine in our arms before May or June, so we need to be very cautious and vigilant.”

Deborah Birx, coordinator of the White House coronavirus task force, similarly urged people not to let their guard down amid news of a coming vaccine.

“I want to be very frank to the American people. The vaccine is critical, but it’s not going to save us from this current surge,” Birx said on NBC News’s “Meet the Press.” “Only we can save us from this current surge. And we know precisely what to do. So, if you have loved ones that you want to protect, you have to follow these guidelines now.”