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.

American biotechnology company Regeneron Pharmaceuticals announced Wednesday that its cocktail of two monoclonal antibodies held up in laboratory experiments against new variants of the novel coronavirus first identified in the United Kingdom and South Africa.

Monoclonal antibodies are synthetic versions of our natural antibody defense to infection. They are being studied as a way to both treat and prevent COVID-19 infection, with promising results. But unlike vaccines, which are thought to offer broader protection, some scientists have been worried that this type of therapy would be less effective against newly emerging variants of the virus.

Wednesday's announcement is good news for Regeneron's monoclonal antibody treatment, REGEN-COV, though the data is still preliminary and currently under peer review.

Regeneron scientists as well as researchers at Columbia University in New York City have each independently confirmed that the casirivimab and imdevimab antibody cocktail successfully neutralized both the U.K. and South Africa variants when tested against them, according to a company press release.

REGEN-COV has not yet been tested against another variant that was first identified in Brazil. However, Regeneron said the two-antibody cocktail "is expected to remain similarly potent" based on some resemblance which the Brazil variant bears to the South Africa strain. The company said it is pursuing further confirmatory research.

It's the latest piece of promising news about the efficacy of monoclonal antibodies as treatment for COVID-19. On Tuesday, American pharmaceutical firm Eli Lilly and Company announced that a combination of two monoclonal antibodies, bamlanivimab and etesevimab, was found to be effective in COVID-19 patients at high risk of severe infection, reducing the risk of hospitalization and death by 70%, according to the results of a final-stage trial.

That same day, Regeneron announced its antibody cocktail had shown positive initial results in prophylactic use -- that is, helping ward off COVID-19 in those who may have been exposed to the virus. Regeneron’s chief scientific officer, Dr. George Yancopoulos, said he hopes the drug "may be able to help break this chain" of active infection and transmission.

Last Thursday, Eli Lilly released data showing bamlanivimab may help prevent disease and stop outbreaks among residents and staff of long-term care facilities.

ABC News' Sasha Pezenik contributed to this report.