The White House said 2.2 million vaccine doses have been administered in the last 24 hours -- the highest single-day total since May.

The Minnesotan man who is confirmed to have the omicron variant of COVID-19 received a booster shot in early November, health officials said.

The man attended an anime convention at the Javits Center in New York City from Nov. 19 to Nov. 21, and then, after experiencing mild symptoms on Nov. 22, he was tested on Nov. 24. He no longer has symptoms.

"It seems quite possible, perhaps, most likely, that the transmission happened at the convention in New York City, but that's not definitive," health officials said.

The Javits Center said everyone is required to show proof of vaccination and wear masks inside.

The individual had no history of international travel, officials said.

One of the man's close contacts has tested positive via a rapid test, officials said. Further tests to determine if the second individual is also positive for the omicron variant have yet to be conducted.

-ABC News' Arielle Mitropoulos

The U.K. reported 53,495 new cases on Thursday – the highest single-day rise since July 17, British health officials said.

Hospitalizations in the U.K. are down 6.5% over the last week while deaths are down 3% over the last week, officials said.

Over 80% of the 12-and-over population is fully vaccinated.

Thirty-two cases of the omicron variant have been detected in the U.K.

-ABC News' Christine Theodorou

As omicron appears to be rapidly overtaking delta as the dominant variant of the novel coronavirus in South Africa, a scientist warned Thursday that the new variant appears to be able to dodge some of the immunity from vaccines and previous infections.

Professor Anne von Gottberg, a clinical microbiologist at South Africa's National Institute for Communicable Diseases, told reporters during an online press briefing that omicron may not be more contagious or virulent than delta, but early data indicates previous infection does not provide protection against omicron as it seems to do with delta.

"We believe that omicron is widespread in the country," von Gottberg said.

South Africa and Botswana were the first countries to identify the omicron variant last month. Since then, South Africa has reported a total of 172 confirmed cases and Botswana has reported 19.

Over the past week, Southern Africa has recorded a spike in COVID-19 infections, hospitalizations and deaths, mostly driven by South Africa, where scientists believe omicron is rapidly becoming the dominant variant.

"It does look like there is a predominance of omicron throughout the country," von Gottberg said. "Almost 80% of specimens being sequenced in November are omicron. So we believe, truly, there is a link in the increase in cases with omicron variant."

At least 10 people have tested positive for COVID-19 on a Cruise Norwegian ship disembarking in New Orleans this weekend, according to the Louisiana Department of Health.

Those infected include both passengers and crew members, officials said.

The Norwegian Breakaway departed from New Orleans on Nov. 28 and stopped in Belize, Honduras and Mexico on its voyage. There are more than 3,200 individuals on board, the health department said.

The company required on-site testing in addition to proof of vaccination before boarding the vessel, according to the Port of New Orleans.

The health department said the cruise line has been adhering to appropriate quarantine and isolation protocols. In addition, everyone aboard the ship will be tested for COVID prior to disembarking.

Those who test positive for COVID-19 on the ship will either travel by personal vehicle directly to their private residence or self-isolate according to current Centers fo Disease Control and Prevention guidelines in accommodations provided by Norwegian Cruise Lines.

"The health and safety of our guests, crew and the communities we visit is our highest priority, and we will continue to take all appropriate actions to ensure their wellbeing and protect public health," a Norwegian Cruise Lines spokesperson told ABC News.

"We have identified a handful of COVID-19 cases among guests and crew onboard Norwegian Breakaway, which is scheduled to disembark in New Orleans, LA on December 5. All of the identified cases onboard are asymptomatic. In addition to requiring that 100% of guests and crew are fully vaccinated, per the Company's comprehensive health and safety protocols, we have implemented quarantine, isolation and contact tracing procedures for identified cases."

The spokesperson said the company is testing all individuals prior to disembarkation, and providing post-exposure and quarantine public health guidance by the CDC.

"Any guests who have tested positive for COVID-19 will travel by personal vehicle to their personal residence or self-isolate in accommodations provided by the Company according to CDC guidelines," the spokesperson said. "We take this matter extremely seriously and will continue to work closely with the CDC, the office of Governor John Bel Edwards, the Louisiana Department of Health as well as the city and port of New Orleans. At this time, there have been no changes to scheduled future sailings on Norwegian Breakaway. We will provide additional updates to impacted guests as appropriate."