Vaccine appointments in New York City will be rescheduled due to a major winter storm heading toward the East Coast.

The nor'easter is expected to begin Sunday night and could dump up to a foot of snow onto the city.

"Last thing we want to do is to urge our seniors to come out in the middle of a storm like this," NYC Mayor Bill de Blasio said at a press conference Sunday morning. "It doesn't make sense."

-ABC News' Joshua Hoyos

The mass COVID-19 vaccination site at Dodger Stadium, one of the largest in the country, was temporarily halted Saturday after the entrance was blocked by anti-vaccine protesters.

The group carried anti-vaccine and anti-mask signs, leading to a long line of cars waiting to get into the stadium, ABC Los Angeles station KABC reported.

The stadium entrance was closed from about 1:50 p.m. to 2:45 p.m., Los Angeles Fire Department Public Information Officer David Ortiz told ABC News. Vaccinations continued inside as the gate was closed, Ortiz said.

A social media post described the demonstration as "SCAMDEMIC PROTEST/MARCH" and advised participants to refrain from wearing pro-Trump or MAGA attire.

"…we want our statement to resonate with the sheeple," the post read, according to The Associated Press. “No flags but informational signs only.”

No arrests were made as a result of the protests.

Republican Arkansas Gov. Asa Hutchinson said Sunday that vaccine distribution has been "seamless" under the Biden administration.

"In terms of the vaccine distribution, it's been seamless. And I was delighted that we had a ... 14% increase in vaccine supply last week. This is going to be very, very important for us. They said they're going to invoke the Defense Production Act. I don't know the details on that, but anything they can do to speed up the production," Hutchinson said on ABC's "This Week."

"Thank goodness we have that partnership which is good with the federal government. And President Biden and his team is -- is working to assure that partnership and not tear it apart, which I'm very grateful for," he told "This Week" Co-anchor Martha Raddatz.

-ABC News' Jack Arnholz

Dave McGillivray, the race director of the Boston Marathon, has been selected by the state of Massachusetts to run the mass vaccination operations at Gillette Stadium and Fenway Park.

McGillivray owns DMSE Sports, which organizes and manages dozens of outdoor events every year. To help keep DMSE Sports afloat, McGillivray connected with CIC Health -- which operates the mass COVID-19 vaccination sites at Fenway Park and Gillette Stadium -- through the state of Massachusetts.

Now, McGillivray is running logistics for both sites.

"For me, the feeling is so good that the thing that knocked us to our knees is now the thing that is allowing us to do good: that we're keeping people healthy, we're saving lives and we're even bringing our own industry back," McGillivray said in an interview with Boston ABC affiliate WCVB().

Fenway Park is the home of the Boston Red Sox, while Gillette Stadium, located in Foxborough, is the home stadium for the New England Patriots. The Gillette Stadium site opened two weeks ago, with Fenway officially opening Monday. Both sites are expected to administer 5,000 doses per day once fully up and running.

The Boston Marathon, usually held in April, has been postponed to October. The in-person event was canceled in 2020, though it was held virtually.

ABC News' Arielle Mitropoulos contributed to this report.

The United States’ first known cases of the South Africa variant of the novel coronavirus have been confirmed in two people in South Carolina, according to the South Carolina Department of Health and Environmental Control.

"There is no known travel history and no connection between these two cases," the department said in a statement Thursday.

Both cases are among adults, one who is from the Lowcountry region and another who is from the Pee Dee region, according to the department.

The U.S. Centers for Disease Control and Prevention said it's aware of the cases and it "recommends that people avoid travel at this time."

The so-called B1351 variant, first identified in South Africa, has been detected in more than 30 countries, according to the South Carolina Department of Health and Environmental Control.

"Experts agree that existing vaccines work to protect us from this variant, even if we don’t know precisely how effective they are," the department said. "At this time, there’s no evidence to suggest that the B.1.351 variant causes more severe illness."

During an interview Thursday on ABC's "Good Morning America," Dr. Anthony Fauci, chief medical adviser to U.S. President Joe Biden and the nation's leading infectious disease expert, said the South Africa variant "troubles" him.

Fauci said lab experiments show the neutralizing antibodies induced by existing COVID-19 vaccines are "diminished by multifold" when tested against the B1351 variant

"It's still within the range of what you would predict to be protective," he said, "but I take no great comfort in that."

However, scientists are already working on vaccines that will specifically target the South Africa variant, according to Fauci.

"May not be necessary," he said, "but if it is we'll already be on the road to be able to give people a boost that directs against the South African isolate."