(Reuters) – U.S. COVID-19 cases are up around 11% over last week, almost entirely among people who have not been vaccinated, officials said on Thursday, as the highly infectious Delta variant becomes the dominant COVID-19 strain in the country.

Around 93% of COVID-19 cases have occurred in counties with vaccination rates of less than 40%, said U.S. Centers for Disease Control and Prevention director Rochelle Walensky.

Nearly all deaths and hospitalizations nationwide are among unvaccinated people, said Jeff Zients, who leads the White House’s COVID-19 response team.

“Simply put: in areas of low vaccination coverage, cases and hospitalizations are up,” Walensky said.

The CDC earlier this week said that the Delta variant of COVID-19 has already become the dominant strain in the United States. The variant, which is highly contagious, has also become dominant in other countries around the world.

Cases of COVID-19 are surging in counties representing 9 million people, Walensky said.

The White House plans to concentrate federal assistance for vaccinating against and treating COVID-19 in states including Arkansas, Missouri, Nevada and Illinois, Zients said.

The White House last week said it would send out special teams to hot spots around the United States to combat the Delta variant amid rising case counts in parts of the country.

The White House is also working to make COVID-19 vaccines available at doctors’ offices around the country, Zients added.

He said the spread of the Delta variant is particularly dangerous to young people. Research suggests it may cause more severe disease among younger people than other variants of the coronavirus.

Walensky added that the United States is seeing outbreaks of COVID-19 at summer camps and other community events.

(Reporting by Carl O’Donnell in New York and Jeff Mason in Washington, D.C.; Editing by Chizu Nomiyama and Mike Collett-White)