By Madeline Holcombe, Jason Hanna and Naomi Thomas, CNN

(CNN) -- Dr. Anthony Fauci wants people who still believe Covid-19 is a hoax to know it's real and that the US needs everyone to get behind public health measures.

Fauci, the longtime director of the National Institute of Allergy and Infectious Diseases, and other health experts have said the next few months will be a challenging time, but Americans can help turn the tide by wearing masks, keeping a distance from others and washing their hands frequently.

However, "trouble is, you go to different parts of the country, and even when the outbreak is clear and hospitals are on the verge of being overrun, there are a substantial proportion of the people who still think that this is not real, that it's fake news or that it's a hoax," Fauci said.

Fauci has advised six presidents. He said he's never seen anything like this.

"We've got to overcome that and pull together as a nation uniformly with adhering to these public health measures," he said at the Wall Street Journal CEO Council summit on Tuesday.

That people aren't doing this is "really extraordinarily frustrating, because we feel strongly that we will be able to have a significant impact," he said.

The US surpassed 15 million total reported Covid-19 cases on Tuesday, meaning one in 22 Americans has tested positive for the virus. Experts feel the actual number of infections is much higher.

Assistant Secretary for Health and Human Services Admiral Brett Giroir told CNN people also should try to stay home for the December holidays.

"The end of the pandemic is in sight," he said. "The vaccine will work. It will end the pandemic and return us to as near normal or normal as possible, but we have to do our part right now, which is those mitigations techniques."

Vice President Mike Pence, speaking at a White House vaccine summit, also told Americans to wear their face coverings and follow other guidelines.

"It's the way we'll see our way through the months ahead between now and when the coronavirus vaccine that will likely be approved this week will be widely available for every American," he said.

More than 2,000 deaths a day recently

The country has averaged about 2,237 daily coronavirus deaths across a week -- just below its highest-ever average of 2,241, set on April 24, Johns Hopkins University data show.

At least 286,189 people have died from Covid-19, according to the data.

Cases and hospitalizations also are soaring, as more physicians and nurses warn they're perilously low on space, staff and energy to take care of burgeoning numbers of patients.

• The number of new daily cases across a week Monday was 201,154 -- a US record high for the pandemic, according to JHU data.

• More than 104,600 Covid-19 patients were in US hospitals on Monday -- the highest figure of the pandemic, according to the COVID Tracking Project.

More than 15 million coronavirus cases have been reported in the US so far -- though researchers have said this is likely a vast undercount, partly because of limited testing capacity, especially early in the pandemic. A CDC modeling study suggested as many as 53 million people in the United States could have been infected from February through September.

Health experts are expecting the spread to worsen, anticipating new waves from December holiday gatherings on top of a surge from Thanksgiving week.

"We probably are just going to start seeing the brunt of what it means when you have people traveling and congregating in seemingly innocent settings," Fauci told CNN on Monday.

The UK, meanwhile, began administering the first vaccine doses in that nation Tuesday. And in the US, the Food and Drug Administration this week and next will consider granting emergency authorization for vaccine candidates from Pfizer and Moderna, respectively.

Anticipating those authorizations, US officials are ramping up plans to distribute vaccines.

Despite challenges to production and distribution, tens of millions of Americans will be vaccinated by January 20, Health and Human Services Secretary Alex Azar said in an interview with Axios that aired Monday

FDA panel confirms Pfizer vaccine's 95% efficacy rate after 2 doses, in new briefing

An advisory committee to the FDA on Tuesday released a document detailing data on Pfizer and BioNTech's Covid-19 vaccine candidate.

The document confirms that the vaccine's efficacy against Covid-19 was 95%, occurring at least seven days after the second dose -- a rate that had been previously reported by Pfizer. The proposed dosing for this vaccine is two 30-microgram doses 21 days apart.

The document also notes that the vaccine appears to provide "some protection" against Covid-19 following just one dose.

However, Pfizer CEO Albert Bourla emphasized Tuesday that the protection after one dose is "not full," and that therefore Pfizer's product is a "two-dose vaccine."

"People need to take two doses to be able to feel confident that they're protected at ... 95% chance of being protected," Bourla said during an International Federation of Pharmaceutical Manufacturers and Associations meeting Tuesday.

The document goes on to detail the safety profile of the vaccine as "favorable" and notes that the most common adverse reactions to the vaccine have been reactions at the injection site, fatigue, headache, muscle pain, chills, joint pain and fever.

The document will be discussed in a meeting on Thursday, during which the FDA's Vaccine and Related Biological Products Advisory Committee will provide recommendations to the FDA on whether the vaccine is effective in preventing Covid-19 in people 16 and older and whether the potential benefits of the vaccine outweigh the risks.

Other vaccine candidates -- those from AstraZeneca and Johnson & Johnson -- are set to complete Phase 3 trials in January and possibly be ready for use in February, Moncef Slaoui, chief scientific adviser of the federal government's Operation Warp Speed vaccine initiative, said Tuesday.

AstraZeneca's vaccine candidate was found to have an average 70.4% efficacy, according to an interim analysis of Phase 3 trial results published in The Lancet journal on Tuesday.

Those findings fall in line with the efficacy that AstraZeneca announced in November.

Recruiting to vaccinate over the holidays

If the vaccines are approved in the US, officials hope to distribute the first wave this month, starting with health care workers and long-term care facility residents. Efforts are underway to distribute and administer them.

Gen. Gustave Perna, chief operating officer of Operation Warp Speed, said Tuesday: "We will start to have shots in arms within 96 hours of EUA. That's what I believe with all my heart."

Mount Sinai Hospital System in New York has begun recruiting people to vaccinate its health care workers over the holiday season, Susan Mashni, vice president and chief pharmacy officer for Mount Sinai health system, told CNN. In addition to nurses, pharmacists and those who are currently administering flu vaccines, they are reaching out to pharmacy and nursing interns, as well as medical students and residents.

The system is planning to administer Pfizer's vaccine in "pods," using makeshift walls and bays in hospital lobbies, and to stagger the immunizations among employees in anticipation that they will feel side effects.