A second storm bringing heavy snow to the Northeast has shut down vaccination sites in at least two states.

New York Gov. Andrew Cuomo and New Jersey Gov. Phil Murphy both announced that appointments for Sunday would be rescheduled due to the inclement weather.

Mass vaccination sites located indoors, such as the newly opened Yankee Stadium, will continue as scheduled as they have the infrastructure and equipment in place to ensure people can safely enter and exit the location, according to ABC New York station WABC.

Nine percent of Americans -- 28.9 million people – have received one or more vaccine doses, according to a report from the Department of Health and Human Services.

Two percent of Americans -- 7.5 million people -- have received two doses, the report said.

Deaths are down 4% since the peak on Jan. 13, while hospital admissions have decreased 37% since the Jan. 9 peak, the report said.

ABC News’ Josh Margolin and Brian Hartman contributed to this report.

New York state’s seven-day average positivity rate has fallen to 4.58% -- the lowest since Dec. 2, Gov. Andrew Cuomo announced Saturday.

New York has 7,804 COVID-19 patients in hospitals -- the lowest since Dec. 27, he added.

Cuomo called these numbers "a reflection of the discipline New Yorkers have shown to defeat the virus."

"Super Bowl weekend is here and while the instinct may be to celebrate together, we cannot get cocky -- we must continue doing the things we know are effective at taming the virus: wear a mask, adhere to social distancing, and avoid gatherings," he said.

ABC News’ Josh Hoyos contributed to this report.

China has given approval for the domestic-made Sinovac Biotech COVID-19 vaccine to be administered to the general public -- not just high-risk individuals and front-line workers.

The National Medical Products Administration shared the news in a statement Saturday.

The vaccine -- which was given emergency approval in China last July -- has already been sold to at least 10 other countries and is being given to people in at least five other countries.

China previously said shots will be given without cost to citizens.

Dr. Stephen Hoge, president of American biotechnolgy company Moderna, said he's hopeful that vaccines can help the U.S. population achieve herd immunity against the novel coronavirus by mid-year.

"It really depends what you think herd immunity needs to be. But if you assume 50 to 70% of the population, then we're working hard ourselves and the other manufacturers to make sure that's a possibility really in the late spring, early summer," Hoge told ABC News chief anchor George Stephanopoulos in an interview Monday on "Good Morning America."

"It's ultimately going to depend upon the delivery of those vaccines, and so that's something that the states and the health care providers in this country are ultimately leading the way on as well as Americans deciding they want to receive that vaccine," he added. But we're optimistic that by the middle of the year, we'll be able to achieve those sorts of numbers."

Moderna is ramping up production of its COVID-19 vaccine and is working to clear any "bottlenecks" in the supply chain, according to Hoge.

"At this point, a lot of the logistical bottlenecks that we're running into are problems we can solve on our own," he noted. "We're in good shape."

Hoge, who was a resident physician in New York City, said data currently shows that existing vaccines are still effective against all emerging strains of the virus. But the variant first identified in South Africa "is of some concern because it looks like it could hide from the vaccine a little better than others," he said.

"So our approach in Moderna is going to be to develop a booster vaccine so that if the South African variant or any other variant becomes a concern, we'll be able to offer a way to identify that, prevent it from hiding from the vaccine," he said.