Half of Americans, including all ages, are now fully vaccinated against Covid-19, a White House official said Friday, a major milestone as the nation battles a surge in new infections fueled by the Delta variant.

More than 821,000 doses were given from the previous day, including 565,000 people receiving their first syringe, White House Covid data director Cyrus Shahpar said in a tweet before the data was posted on the Centers for Disease Control and Prevention website were published. The seven-day average of new vaccinations is up 11% from last week and 44% over the past two weeks, he added.

While the milestone is exciting, the country still has a long way to go before the pandemic is over, said Dr. Paul Offit, who advises the Food and Drug Administration on Covid vaccines. The highly contagious Delta variant continues to spread rapidly, especially in regions of the country with the lowest vaccination rates, he said.

“They had over 100,000 cases and over 600 deaths yesterday, which tells us we’re not there yet,” Offit said.

The U.S. reports an average of about 98,500 daily infections, data compiled by Johns Hopkins University shows, which already surpassed the peak of cases seen last summer when the nation lacked a vaccine.

Florida, Texas, Missouri, Arkansas, Louisiana, Alabama, and Mississippi – states with some of the lowest vaccination rates – accounted for roughly half of the new Covid cases and hospital stays in the past week, said Jeffrey Zients, the White House’s Covid Response Coordinator, said told reporters Thursday. In the past seven days, 1 in 3 new Covid cases occurred in Florida and Texas.

In Florida, where Governor Ron DeSantis opposes calls for further restrictions, the infection rate is nearing the state’s pandemic peak in late January, when an average of nearly 18,000 new cases were reported each day.

Florida reports an average of about 15,800 new cases daily for the past seven days, according to data compiled by Johns Hopkins University, 51% more than a week ago. This is the second worst outbreak in the US by average daily new cases per capita, behind Louisiana.

The death toll there is also rising, with an average of 58 daily Covid deaths, 45% more than last week but below the record seven-day average of more than 180 daily deaths in late January.

The outbreak threatens to slow the country’s progress in ending the pandemic, especially as schools reopen and employers start bringing workers back to the office this fall, health experts say.

With the virus widespread in states like Florida, the nation “is likely to see even more worrying varieties emerge this fall and winter,” said Lawrence Gostin, director of the World Health Organization’s Collaborating Center on National and Global Health Law.

“America is about to return to normal. This could be a major setback for our national Covid response, ”he said.

As cases rise, more companies are requiring their workers to get vaccinated, and federal health officials say they are urging states to incentivize their residents.

Some Americans are already seeing the effects of not vaccinating and are now getting the injections, US officials said Thursday.

In Arkansas, Mississippi, Louisiana, and Alabama, the seven-day average of first-doses reported daily has more than doubled since early July, CDC data shows, as the outbreak worsened nationwide. In Arkansas, which has the third worst outbreak in the country, based on new cases per capita every day, vaccinations nearly tripled.

Zients said Thursday that the White House’s Covid Surge Response Teams are also working with 16 states with rising cases to meet their specific needs.

– CNBC’s Nate Rattner contributed to this report.