March 1 (UPI) -- There were 51,200 new coronavirus cases in the United States on Sunday -- the fewest since the middle of October, according to updated data from Johns Hopkins University.
The data show about 1,300 COVID-19 deaths on Sunday.
The low mark for new cases since Oct. 18 punctuates a steady decline in cases that began in early January, when the United States was seeing more than 200,000 new cases each day and more than 4,000 related deaths on some.
Since the start of the pandemic more than a year ago, there have been a total of 28.61 million cases and 513,100 related deaths, according to Johns Hopkins.
The national distribution of vaccines has been a key factor in the declining cases, experts say. A third vaccine -- Johnson & Johnson's one-shot formulation that has proven to be about 85% effective in preventing severe cases -- has already entered distribution.
"This is very important because if you look at other countries, such as South Africa where you have the B1351 [variant], you can see that the efficacy against severe critical disease was 82% there," Dr. Anthony Fauci, President Joe Biden's chief medical adviser, said at a White House briefing Monday.
"So even though the vaccine itself was not specifically directed against those variants, it did extremely well when it came to preventing severe critical disease."
The new adenovirus-based vaccine is manufactured by Johnson & Johnson subsidiary Janssen.
"This means we now have three safe and highly effective vaccines that prevent serious illness, hospitalization, and death from COVID-19," Walensky said at the briefing.
"The Janssen vaccine is a much-needed addition to our toolbox and increases the number of vaccine doses available, and makes it possible for people to get -- for more people to get vaccinated and protected."
"Johnson & Johnson doses will be delivered as early as tomorrow," Zients added, noting that federal officials began to distribute 4 million doses of the new vaccine on Sunday.
Walensky noted the advantages of the new vaccine, in that it doesn't require a booster and it can be stored and shipped at much warmer temperatures than either of the vaccines by Pfizer and Moderna.
"I know that many Americans look forward to rolling up their sleeves with confidence as soon as a COVID-19 vaccine is available to them," she said. "We are working hard to get and distribute these vaccines to your communities."
Walensky, however, voiced concern that the decline of new U.S. cases may be stalling at a higher-than-expected level.
"Stalling at over 70,000 cases a day," she said. "I am really worried about reports that more states are rolling back the exact public health measures we have recommended to protect people."
With the start of March on Monday, several states ushered in new phases of coronavirus-related restrictions.
In Virginia, Gov. Ralph Northam eased some restrictions, including lifting a statewide midnight curfew and allowing alcohol sales at bars to continue until midnight. Also, outdoor entertainment venues can operate at 30% capacity.
Indoor restrictions remain in Virginia, and overnight outdoor summer camps can open on May 1.
In California, health provider Blue Shield took over distribution of all vaccines in California.
"[March] marks the start of California's transition to an enhanced provider vaccination network that's designed to make COVID-19 vaccines available to all Californians equitably, safely and as quickly as possible," the company said.
Previously, vaccine protocol has been managed from county to county in California, which has caused statewide frustration. The change by state leaders introduces a uniform protocol under Blue Shield distribution.
In Florida, the state's largest grocery store chain, Publix, begins offering vaccines at all of its pharmacies in Miami-Dade and Broward counties -- the state's top two most populous, with more than 4.5 million people.
Also, Broward Health, one of South Florida's largest hospital systems, opens vaccines to anyone over the age of 18 who meet one of the high-risk categories.