The number of COVID-19 deaths in the U.S. increased dramatically in the past week, according to an internal memo from the U.S. Department of Health and Human Services obtained by ABC News Thursday night.

There were 16,237 deaths recorded from Dec. 4-10, marking a 44.3% increase in new deaths compared with the previous seven-day period, the memo said.

There were 1,449,322 new cases confirmed during that period -- a 26.9% increase week-over-week, according to the memo.

Across the country, 30% of hospitals have more than 80% of their intensive care unit beds filled, and 31% of ventilators in use are occupied by COVID-19 patients, HHS said.

Several states are seeing hospital strain.

COVID-19 hospitalizations in Nevada doubled from mid-October to mid-November, and projections show hospital capacity being surpassed in the next 30 days, HHS said.

In Pennsylvania, the seven-day hospitalization rate hit a new four-month peak on Dec. 6, and officials warned that hospitals will be overwhelmed if residents do not take precautions, the memo said.

-ABC News' Josh Margolin

The U.S. had its "worst week yet" during the pandemic in terms of COVID-19 deaths, according to an analysis by the COVID Tracking Project.

The seven-day average of reported deaths per day surpassed 2,000 this week for the first time since the spring. As of Dec. 9, that number was 2,281, a new record.

New COVID-19 deaths also set a record high this week, with 3,088 reported on Thursday.

As the number of new cases and current hospitalizations continue to climb, "the worst is yet to come," the COVID Tracking Project warned.

"Given the rapid increase in the number of new cases, we expect the metrics for hospitalizations and deaths to continue to rise in the coming weeks -- especially if in-person gatherings over Thanksgiving led to increased spread of the novel coronavirus, as public health experts warned," it said.

An independent advisory panel of infectious disease experts, doctors and scientists recommended Thursday that the U.S. government authorize the nation's first vaccine for people over the age of 16.

It's a major milestone in the effort to get the vaccine to hospitals and pharmacies.

After hours of drilling down into data produced from a clinical trial involving 44,000 people, the group of experts -- known as the Vaccines and Related Biological Products Advisory Committee -- voted in favor of the vaccine for people over 16 years of age.

Several members raised concerns about unknowns about the vaccine, including its potential to trigger allergic reactions and little data on how it impacts pregnant women.

Several panel members also expressed concern there wasn't enough data to support giving the vaccines to 16- and 17-year-olds.

At issue was this question: "Based on the totality of scientific evidence available, do the benefits of the Pfizer-BioNTech COVID-19 Vaccine outweigh its risks for use in individuals 16 years of age and older?"

The panel voted 17-4 that the benefits outweighed the risks. One member of the committee abstained.

The U.S. Food and Drug Administration will now take the committee's input into account in issuing an emergency use authorization.

-ABC News' Anne Flaherty

Indoor dining and gyms will be suspended in Pennsylvania beginning Saturday, Gov. Tom Wolf announced.

Indoor gatherings will be limited to 10 people, he said.

Wolf announced the new restrictions one day after revealing that he tested positive for COVID-19.

Pennsylvania has over 422,000 confirmed cases and has lost at least 12,010 residents to the virus.

U.S. Surgeon General Jerome Adams urged people to take the coronavirus pandemic seriously and follow public health guidelines as infections and hospitalizations soar across the country.

"I want the American people to know this virus is incredibly unforgiving, cases are going up, hospitalizations are going up, my colleagues are dog-tired and we need you to hang on just a little bit longer because we've got vaccines coming but we want as many people to be alive to get them as possible and a lot of that is going to depend on your behavior," Adams told ABC News chief anchor George Stephanopoulos in an interview Monday on "Good Morning America."

Although "more people than ever are wearing masks," Adams said he's "very" concerned by the number of people who still "don't understand how much spread is occurring by people who don't have symptoms."

About 20 million "full doses" of COVID-19 vaccines will be available by the end of the year, according to Adams, who urged every American to be immunized against the virus as soon as a vaccine is authorized and made available.

"It's a way that we can ultimately end this pandemic, but it doesn't matter if people won't get the vaccination," the surgeon general said. "We know that vaccine levels are only about 50% for adults for flu and they go down to about 40% for African-Americans."

Adams said he is working with historically black colleges and universities as well as faith communities to bolster vaccine confidence among all populations. The White House is also hosting a vaccine summit Tuesday, he said.

"One thing you can all do right now, it's national flu immunization week, get your flu shot because half a million people were hospitalized last year with the flu," Adams said. "We simply can't afford for that to happen this year with hospitals being overwhelmed."

The surgeon general said the current surge in infections across the country "is different than earlier surges," because it's not about a lack of masks or personal protective equipment, nor is it due to a lack of testing.

"It's really about health care capacity, and certain places are just being overwhelmed," he said. "So we know that we can actually help them with their health care capacity by immunizing their health care staff. We're going to leave it up to the states, but we're going to give them guidance."

Adams noted it's also important to vaccinate those who are most likely to die from COVID-19.

"We know that 40 to 50% of the deaths are occurring in people who are in longterm care facilities who are older," he said.