There were 142,511 new cases of COVID-19 confirmed in the United States on Tuesday, according to a real-time count kept by Johns Hopkins University.

Tuesday's case count is far less than the country's all-time high of 298,031 newly confirmed infections on Jan. 2, Johns Hopkins data shows.

An additional 3,990 fatalities from COVID-19 were registered nationwide on Tuesday, down from a peak of 4,462 new deaths on Jan. 12, according to Johns Hopkins data.

COVID-19 data may be skewed due to possible lags in reporting over the Martin Luther King Jr. Day holiday weekend.

A total of 25,443,700 people in the U.S. have been diagnosed with COVID-19 since the pandemic began, and at least 425,216 have died, according to Johns Hopkins data. The cases include people from all 50 U.S. states, Washington, D.C., and other U.S. territories as well as repatriated citizens.

Much of the country was under lockdown by the end of March as the first wave of pandemic hit. By May 20, all U.S. states had begun lifting stay-at-home orders and other restrictions put in place to curb the spread of the novel coronavirus. The day-to-day increase in the country's cases then hovered around 20,000 for a couple of weeks before shooting back up over the summer.

The numbers lingered around 40,000 to 50,000 from mid-August through early October before surging again to record levels, crossing 100,000 for the first time on Nov. 4, then reaching 200,000 on Nov. 27 before nearing 300,000 on Jan. 2.

So far, the U.S. Food and Drug Administration has authorized two COVID-19 vaccines for emergency use -- one developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech, and another developed by American biotechnology company Moderna and the National Institute of Allergy and Infectious Diseases.

COVID-19 hospitalizations in the United States continue to trend downward, but the country's daily death rate is still above 3,000, according to The COVID Tracking Project, a volunteer-run effort to track the U.S. outbreak.

There are 108,957 people currently hospitalized with COVID-19 in the U.S., which is almost 30,000 fewer cases than a couple of weeks ago, the group said.

The country's seven-day average of daily COVID-19 deaths is now at 3,302, according to The COVID Tracking Project.

"While cases and hospitalizations are falling, the 7-day average for deaths jumped up today. That's because last Tuesday's data was depressed by the holiday," the group wrote on Twitter Tuesday. "We do expect, however, that deaths could stay elevated for quite a while."

U.S. President Joe Biden's administration said it has secured commitments from manufacturers to buy another 200 million doses of COVID-19 vaccines to arrive this summer -- 100 million from Pfizer and 100 million from Moderna.

This raises the total to 600 million and ensures the U.S. will eventually have two shots for nearly every American.

"We expect these vaccines to be available in production over the course of the summer," a Biden official said Tuesday.

Buying more doses had always been an option for the U.S. government as part of the prior contracts.

"We will increase overall weekly vaccination distributions of states, tribes and territories from 8.6 million doses to a minimum of 10 million doses starting next week," Biden said Tuesday.

The president also vowed to increase "transparency with states, cities and tribes and local partners when it comes to the vaccine supply."

"From this week forward," he said, "states, tribes and territories will now always have a reliable, three-week forecast with the supply they're going to get."

ABC News’ Anne Flaherty contributed to this report.

U.S. Vice President Kamala Harris, while wearing two face masks, received her second COVID-19 vaccine dose on Tuesday at the National Institutes of Health in Bethesda, Maryland.

Harris described the shot as "relatively painless," adding, "We’re going to get 100 million vaccinations in 100 days."

"I want to urge everyone to take the vaccine when it is your turn," she said.

Harris' husband, second gentleman Doug Emhoff, also received his second vaccine dose Tuesday.

Dr. Anthony Fauci, the nation's leading infectious disease expert, spoke about the latest updates on the U.S. vaccine rollout during an interview Monday on ABC News Live.

Fauci, director of the National Institute of Allergy and Infectious Diseases, said that he believes the vaccine will be available to everyone beginning in April, but it won't be until the fall that everyone has actually gotten their shot in the arm.

"It will take several months-May, June, July, August- before you really get what I would consider the herd immunity level, which is an estimate, but I think it's a reasonable estimate, namely getting 70 to 85% of the population vaccinated," Fauci, who is also Biden's chief medical adviser, told ABC News Live.

Fauci said that the timeline is not considering a future approval of coronavirus vaccines developed by Johnson & Johnson and AstraZeneca.

"I think if the J&J or the [AstraZeneca] product comes through with an efficacy that's good enough to be able to be in the mix, that will be very helpful to get things done even sooner than we thought," he said.

Fauci also opened up about an incident where he was exposed to a powder substance that was in his mail last year. The powder was later deemed benign, but only after his security detail put on hazmat suits and sprayed him down.

"It frightened the heck out of my children when they found out about it and my wife too," he said. "I mean, I've decided I'm doing something that might be dangerous but that's it, I chose it. My children did not choose that."

Watch Fauci's full interview with ABC News Live at 7 p.m. and 9 p.m. ET Monday.