The possibility of obtaining herd immunity by the time summer is over and a new school year begins may be an "ambitious goal," Vivek Murthy, President Joe Biden's nominee for U.S. surgeon general, told George Stephanopoulos on "This Week" Sunday.

"I think what -- I think we can see improvement," Murthy said. "I think we can see reductions in cases and hospitalizations and deaths. I think we can see many more people immunized."

The "important thing" will be getting as many people vaccinated as possible, Murthy added.

"The more people we vaccinate, the better we will do, the fewer outbreaks we will see, the sooner we can get back to our way of life," he said.

Murthy also emphasized the importance of dispelling misinformation as well as continuing to take the necessary precautions, such as wearing masks and avoiding indoor gatherings.

"Then I think we can be on a path to not only turning the pandemic around, but, most importantly, getting our schools open, our workplaces back up and running, and regaining our way of life," he said.

The U.S. has surpassed 25 million cases of COVID-19, according to a Johns Hopkins University tally.

The national total confirmed case count currently sits at 25,003,695.

Last week, the U.S. surpassed 400,000 deaths from the virus. The death toll is currently at 417,463 in the U.S. and at 2,122,766 worldwide.

The number of global confirmed cases is nearing 100 million, currently sitting at 98,853,428.

-ABC News’ Joshua Hoyos

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.

The University of Michigan has paused all athletics, including men's and women's basketball, for at least 14 days following "several" positive tests by people within the Michigan Athletic Department. The positive tests were also for the so-called U.K. variant, a more-contagious version of the virus. The decision to pause athletics was made in part due to the fact the tests were for the B.1.1.7 variant.

The decision was made not by the school but by the Michigan Department of Health and Human Services. The athletic programs will not be able to play or practice during the period.

"Canceling competitions is never something we want to do, but with so many unknowns about this variant of COVID-19, we must do everything we can to minimize the spread among student-athletes, coaches, staff, and to the student-athletes at other schools," Athletic Director Warde Manuel said in a statement.

The Wolverines men's basketball team, which is currently ranked No. 7 in the latest Associated Press poll, last played Friday against Purdue. Michigan won, 70-53, to advance to 13-1. They currently lead the Big Ten Conference at 8-1. They were supposed to play on Wednesday at Penn State.

The women's basketball team, currently 10-1 overall and ranked No. 11, was supposed to play Purdue on Sunday. The powerhouse men's ice hockey program, ranked in the top 10 nationally, will be affected as well.

The school said no determination has been made on how games scheduled to be played through Feb. 7 will be impacted.

Twenty-three reports of suspected deaths associated with COVID-19 vaccines have been submitted to Norway's national health registry as of Jan. 14, according to an updated statement from the country's drug regulator on Monday.

The Norwegian Medicines Agency said it "cannot rule out that adverse reactions to the vaccine occurring within the first days following vaccination (such as fever and nausea) may contribute to more serious course and fatal outcome in patients with severe underlying disease."

Thirteen of those reports have been assessed by the drug regulator, as well as the Norwegian Institute of Public Health.

"The reports suggest that common adverse reactions to mRNA vaccines, such as fever and nausea, may have contributed to a fatal outcome in some frail patients," Sigurd Hortemo, chief physician at the Norwegian Medicines Agency, said in the statement.

Steinar Madsen, medical director of the Norwegian Medicines Agency, told the state-run broadcaster NRK: "We are not alarmed by this."

"It is quite clear that these vaccines have very little risk, with a small exception for the frailest patients," Madsen said. "Doctors must now carefully consider who should be vaccinated. Those who are very frail and at the very end of life can be vaccinated after an individual assessment."

Norway is currently administering COVID-19 vaccines to the elderly and people in nursing homes with serious underlying diseases -- at first with just the Pfizer/BioNTech vaccine up until Jan. 15, and then also with the Moderna vaccine. Official figures show that more than 30,000 people have received the first shot of the Pfizer or Moderna vaccines in Norway since the end of December.

According to the Norwegian Medicines Agency, an average of 400 people die each week in nursing homes and long-term care facilities nationwide.

The Scandinavian country of 5.3 million people has confirmed more than 58,000 cases of COVID-19 since the start of the pandemic, including at least 521 deaths, according to the latest data from the Norwegian Institute of Public Health.