Norway's national public health institute said Tuesday that there is currently no correlation between receiving the Pfizer/BioNTech vaccine and an increased risk of death among 23 people who died after getting the shot.

The deceased were "severely frail patients" who died within six days after vaccination in the Scandinavian country, and the incidents "do not imply a casual relationship between COVID-19 vaccination and death," according to Dr. Sara Viksmoen Watle, chief physician at the Norwegian Institute for Public Health.

"When we vaccinate the eldest and sickest who often have several underlying conditions we expect high mortality in this population. Hence, we also expect deaths following vaccination," Watle said in a statement Tuesday. "We do not yet know if these deaths are due to the vaccine or other causes, but we cannot exclude that common side effects may have led to a more severe course for some patients."

The Norwegian Medicines Agency and the Norwegian Institute of Public Health are investigating the deaths.

"So far, there are no statistical analyses that indicate that coronavirus vaccination has had an increased risk of death among those vaccinated," Watle said, after noting that the fatal incidents will be examined "in relation to the expected number of deaths among the nursing home population."

"In order to be able to interpret this information, it is important to see the full picture," she added. "Nursing home residents are at very high risk of a severe disease course or dying from COVID-19, and have therefore been prioritised for vaccination. A large proportion of those who live in nursing homes have severe underlying conditions or are in the last stages of life. Life expectancy in nursing homes is relatively short and on average, more than 300 people die in Norwegian nursing homes every week."

U.S. President-elect Joe Biden's pick to lead the Centers for Disease Control and Prevention said she will "hit the ground running" and suggested there might be more travel restrictions in store.

"We need to reset the stage here. We need to make sure the country, the people understand that this pandemic is now going to be addressed with science, with trust, with transparency, with communication of exactly where we are to the American people," Dr. Rochelle Walensky told ABC News chief anchor George Stephanopoulos in an interview Tuesday on "Good Morning America."

Walensky, the chief of infectious diseases at Massachusetts General Hospital in Boston and a professor of medicine at Harvard Medical School, will be sworn in Wednesday as director of the CDC -- an appointment that does not require Senate confirmation.

"I will be sworn in tomorrow, but the work has been happening since I was named," Walensky said, "and we've been working really hard to make sure we can come in and hit the ground running and make sure that we can get this country back to health."

Walensky said the incoming administration's plan to vaccinate 100 million people against COVID-19 within the first 100 days of Biden's presidency is "really ambitious but doable." The key is making sure there are enough people on the ground to administer the vaccines, understanding the supply and how many doses are going to which states, and making vaccines accessible to all people.

"All of that plan is underpinned with equity," Walensky said. "We need to make sure that we're equally and equitably getting the vaccine across this country."

In one of his last orders, outgoing President Donald Trump announced Monday night that he was rescinding entry bans imposed because of the coronavirus pandemic on most visitors from Brazil, the United Kingdom and much of Europe effective Jan. 26. However, Biden's incoming White House press secretary, Jen Psaki, said the new administration won't be lifting the bans.

Walensky agreed with the move to reject Trump's proclamation and said there may be more travel restrictions introduced.

"If you look at the fatalities of 400,000 that we're likely to hit today, if you look at our cases across this country, I don't think now is the time to encourage people to get on international fights, to encourage people to mobilize," Walensky said. "I think now is the time to really buckle down, double down our efforts. And so I don't expect that we'll be lifting travel restrictions and, if anything, I think we can expect that they might tighten, especially in the context of variants that we're hearing about."

Israel confirmed 10,222 new cases of COVID-19 on Monday, its highest daily tally since the pandemic began, suggesting the country's mass vaccination campaign hasn't kicked in yet.

The record figure translates to a nationwide positivity rate in COVID-19 tests of 10.2% However, one promising sign is that the number of critically ill patients hospitalized with COVID-19 across Israel has remained steady over the past few days.

Israel's cumulative totals now stand at 562,167 confirmed cases and 4,049 deaths from the disease, according to the latest data from the Israeli Ministry of Health.

Official figures show 25% of Israel's general population -- nearly 2.2 million people -- have received the first of two doses of a COVID-19 vaccine, while 5% -- more than 420,000 -- have received their second dose.

The Israeli government is expected to meet Tuesday afternoon to determine whether to extend the current lockdown, which has been in place since Jan. 8 and is slated to end Jan. 21.

ABC News' Bruno Nota contributed to this report.

An estimated one in eight people in England have already been infected with the novel coronavirus, according to antibody data from the U.K. Office for National Statistic's COVID-19 Infection Survey.

The survey estimates that 12.1% of the population in England would have tested positive for antibodies against SARS-CoV-2 on a blood test in December 2020, suggesting they had the infection in the past.

"The estimate is weighted to be representative of the overall population and suggests that an average of 5.4 million people aged 16 years and over in England would have tested positive for antibodies to SARS-CoV-2 during this time," the report said. "This equates to 1 in 8 people aged 16 years and over."

That estimate was one in 10 people in Wales, one in 13 people in Northern Ireland and one in 11 people in Scotland, according to the survey.

Meanwhile, a regional analysis of antibody data for England found that the highest positivity was seen in Yorkshire and The Humber, followed by London and the North West, according to the survey.

The survey, which was launched in the United Kingdom in mid-April of last year, measured several factors: how many people test positive for COVID-19 at a given point in time, regardless of whether they report experiencing symptoms; the average number of new infections per week over the course of the study; and the number of people who test positive for antibodies, to indicate how many people are ever likely to have had the infection.

The U.K. -- an island nation of 66 million people made up of England, Scotland, Wales and Northern Ireland -- has confirmed more than 3.4 million cases of COVID-19 since the start of the pandemic, including more than 89,000 deaths. There were 37,535 new cases and 599 additional fatalities from the disease confirmed in the last 24 hours, according to the latest data published on the U.K. government's website.

There have now been more than 20 million vaccine doses given out in the U.S., the CDC reported on Saturday.

The milestone was reached 23 days after the goal set by former President Donald Trump administration's Operation Warp Speed to reach that number of doses by the end of 2020.

President Joe Biden's administration has pledged to distribute 100 million doses in the first 100 days, as well as ramp up production of materials to administer vaccines amid an increase in demand and shortages of supply at the state level.

-ABC News' Ahmad Hemingway contributed to this report.