The United States has reported approximately 19.6% of the world's COVID-19 deaths.

Just over a month after exceeding 300,000 confirmed deaths from the disease, the country is on track to hit yet another staggering milestone: 400,000 deaths in less than a year, according to data collected by Johns Hopkins University.

To put that in perspective, 400,000 people could fill New York City's Madison Square Garden nearly 20 times over, or is roughly equivalent to the entire population of Tampa, Florida, or Tulsa, Oklahoma. The figure is more than the number of American soldiers who died in battle during World War I, World War II and the Vietnam War combined, according to a data estimate compiled by the U.S. Department of Veterans Affairs.

During a White House coronavirus task force press briefing on March 29, President Donald Trump said that if the U.S. could keep its COVID-19 death toll between 100,000 to 200,000, it would mean that his administration had done "a very good job."

But the death toll has already far surpassed the task force's early estimates, and now President-elect Joe Biden's incoming administration is warning that the "dark winter" is not over yet. Dr. Rochelle Walensky, whom Biden has nominated to serve as the next director of the U.S. Centers for Disease Control and Prevention, told CBS's "Face the Nation" on Sunday that they "expect half a million deaths in this country" from COVID-19 by mid-February.

The U.S. is currently averaging over 3,300 new COVID-19 deaths per day. The country has registered more than 52,000 deaths from the disease just since the start of the month, which is approximately one American death from COVID-19 reported every 30 seconds.

However, COVID-19 hospitalizations nationwide appear to be stabilizing. The number of patients hospitalized with the disease across the country continues to drop, now standing at 124,387. Arizona, Nevada and Alabama currently hold the highest COVID-19 hospitalizations rates per million people in the country.

ABC News' Brian Hartman and Arielle Mitropoulos contributed to this report.

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.

California's top epidemiologist has recommended pausing the administration of COVID-19 vaccines from Moderna's lot 041L20A due to "possible allergic reactions" that are under investigation.

"A higher-than-usual number of possible allergic reactions were reported with a specific lot of Moderna vaccine administered at one community vaccination clinic," Dr. Erica Pan, state epidemiologist for the California Department of Public Health, said in a statement late Sunday night. "Fewer than 10 individuals required medical attention over the span of 24 hours. Out of an extreme abundance of caution and also recognizing the extremely limited supply of vaccine, we are recommending that providers use other available vaccine inventory and pause the administration of vaccines from Moderna Lot 041L20A until the investigation by the CDC, FDA, Moderna and the state is complete."

The California Department of Health said all of the affected individuals appeared to be experiencing "a possible severe allergic reaction during the standard observation period," which the U.S. Centers for Disease Control and Prevention says some people have experienced when receiving a COVID-19 vaccine.

More than 330,000 doses from that specific lot have been distributed to 287 providers across the state, with the shipments arriving between Jan. 5 and 12, according to the California Department of Public Health, which said it has not been notified of any other cluster or individual events related to this lot.

When asked for comment, a spokesperson for Moderna told ABC News: "Moderna acknowledges receiving a report from the California Department of Public Health (CDPH) that a number of individuals at one vaccination center in San Diego were treated for possible allergic reactions after vaccination from one lot of Moderna’s COVID-19 Vaccine. The company is fully cooperating with CDPH in investigating these reported adverse events. Consistent with the statement from CDPH, at this point Moderna is unaware of comparable adverse events from other vaccination centers which may have administered vaccines from the same lot."

ABC News' Sony Salzman contributed to this report.

Before the end of the month, London will begin piloting COVID-19 vaccination sites that will be open 24 hours a day, seven days a week, according to Nadhim Zahawi, the United Kingdom's minister for COVID-19 vaccine deployment.

England's National Health Service (NHS) will trial the round-the-clock vaccination sites at hospitals in the British capital.

"And we'll look at how we expand that," Zahawi told Sky News in an interview Monday.

Zahawi said the key with 24-hour vaccination sites is to ensure vulnerable populations, such as people over 80 and others deemed high-risk, are still being targeted.

"At the moment, the challenge is obviously supply -- limited supply vaccine that needs to get into the arms of the most vulnerable four cohorts. So the targeting has to be really, really precise so that we can protect them by mid-February," he added.

"So if you just want to chase volume, chase speed and not accuracy, 24 hours works really well," he continued. "If you want to chase both accuracy, protecting the most vulnerable and of course speed, then you want to do what we're doing which is primary care networks, hospitals, large vaccination centers and of course pharmacies."

As of Saturday, 3,857,266 people in the U.K. have received the first of two doses of a COVID-19 vaccine, according to the latest data published on the U.K. government's website.

The U.K. Medicines and Healthcare products Regulatory Agency (MHRA) has approved three COVID-19 vaccines for use to date -- one developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech, a second developed by England's University of Oxford and British-Swedish pharmaceutical company AstraZeneca, and a third developed by American biotechnology firm Moderna.

The U.K. -- an island nation of 66 million people made up of England, Scotland, Wales and Northern Ireland -- has confirmed more than 3.3 million cases of COVID-19 since the start of the pandemic, including over 89,000 deaths. There were 38,598 new cases and 671 additional deaths confirmed over the past 24 hours, according to the latest data.