The U.S. has seen 864,000 vaccinations in the last 24 hours, the highest daily number since July 3, White House coronavirus response coordinator Jeff Zients said Thursday.

Among those 864,000 vaccinations were 585,000 first shots -- the highest since July 1.

Zients said "Louisiana, Arkansas, Missouri, Alabama, Oklahoma and Mississippi are now vaccinating people at a pace not seen since April."

Tennessee has seen a 90% increase in first shots over the past two weeks and Georgia has recorded a 66% increase in first shots in the last two weeks.

However, seven states -- Florida, Texas, Missouri, Arkansas, Louisiana, Alabama and Mississippi – which have some of the lowest vaccination rates, "account for about half of new cases and hospitalizations in the past week, despite making up less than a quarter of the U.S. population," Zients said.

-ABC News’ Cheyenne Haslett

Yelp now has a feature that will allow businesses to list if they have vaccine requirements.

The feature was mentioned at the White House's COVID-19 briefing Thursday.

-ABC News’ Cheyenne Haslett

In Arkansas, one of the states hit hardest by the delta variant, Gov. Asa Hutchinson has reversed course, asking the legislature to meet for a special session to lift a previously signed ban on mask mandates.

Hutchinson told "Good Morning America" Thursday that masks are not needed in schools if students are vaccinated but he's "particularly concerned" about kids under 12 who are too young to get the shot.

In those cases, he said, schools should have the option to enforce masks.

The governor added that he's pushing vaccine efforts with high school students and "making sure the faculty is vaccinated."

Moderna says its vaccine is 93% effective against symptomatic illness after six months (though this data collection ended before delta emerged in the U.S.).

Moderna said its booster candidates also demonstrate robust antibody responses to variants of concern, including delta.

Moderna President Dr. Stephen Hoge told "Good Morning America" Thursday that the Moderna vaccine offers protection from delta right after receiving it, but it's not known yet if that'll hold up through the winter. He called winter "the biggest test of that vaccine which is why we need to be vigilant and careful."

Hoge said he thinks booster shots will be needed and that the company is "preparing options," but he added that that'll be for public health officials, not the company, to decide.

He also noted that Moderna's goal is to be vaccinating kids under 12 by the end of the year. Moderna isn’t authorized for kids ages 12 to 17 yet, but Hoge hopes authorization could come “any day.”

In Louisiana, which has the nation's highest case rate per 100,000 residents, COVID-19 hospitalizations are reaching peak levels, with more than 1,700 patients now receiving care.

"We're seeing people that are way too young to be so sick," David Wrightson, a respiratory therapist and ECMO (extracorporeal membrane oxygenation) specialist for the Willis-Knighton Health System in Shreveport, Louisiana, told ABC News. "We see families destroyed. We see children without one or more parent because of this virus. We see a new mom who will never go home to see her newborn, will never see her child grow up."

He went on, "When you see someone that's 30 years old with no medical problems at all, nobody knew anything was wrong, and we have this person literally on death's doorstep, doing everything in our power to turn them around and return them to their family. The vaccine is something worth getting."

More people need to see and understand the reality of this disease, he said.

"I wish I could show them a few steps in our day to see what we see and to see what we have to do, and to go home at night and, and have nightmares about those things, and sometimes cry yourself to sleep," he said.

-ABC News’ Erica Baumgart and Arielle Mitropoulos