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.

Despite rising COVID-19 infections in Japan, International Olympic Committee president Thomas Bach said Thursday that there is "no reason whatsoever" to believe the Olympic Games in Tokyo will not open on July 23 as planned.

"This is why there is no plan B and this is why we are fully committed to make these games safe and successful," Back told Japanese news agency Kyodo in an interview Thursday.

However, Bach admitted he could not guarantee that the stands would be full or rule out the possibility that the Games would be held without spectators, according to Kyodo.

The 2020 Summer Olympics were supposed to kick off in Tokyo last year on July 24. But in late March, amid mounting calls to delay or cancel the upcoming Games, the International Olympic Committee and Japan's prime minister announced that the event would be held a year later due to the coronavirus pandemic.

Now, Japan is facing a resurgence of COVID-19. The country of 126 million people reported the highest number of new cases in the Western Pacific region last week. The infection rate -- currently at 32.8 cases per 100,000 people -- increased by 4% over the previous week, according to the World Health Organization's latest COVID-19 weekly epidemiological update.

The Japanese Ministry of Health, Labor and Welfare confirmed 5,662 new cases of COVID-19 as well as an additional 87 fatalities from the disease on Thursday, bringing the cumulative totals to 348,646 cases and 4,829 deaths.

Japanase Prime Minister Yoshihide Suga has declared a state of emergency in Tokyo and 10 other prefectures due to climbing case counts and growing death tolls.