'Steady increase' in vaccines in past month, White House says

An internal Centers for Disease Control and Prevention brief published by the Washington Post Thursday reveals more details about why the delta variant is different to and more concerning than other strains of the coronavirus.

The CDC said the main differences between the delta variant and previous strains is that delta is highly contagious and likely more severe. Plus, breakthrough infections caused by delta may be as transmissible as unvaccinated cases.

"This is an incredibly, incredibly contagious version of virus, it's almost like a whole different virus," Dr. Ashish Jha said. "And CDC is estimating that it is probably also more deadly."

Vaccines prevent more than 90% of severe diseases, but may be less effective at preventing infection or transmission of the delta variant, the CDC said. Therefore, there could be more breakthrough infections and more community spread despite people's vaccination status.

"Current vaccines continue to provide strong protection against severe illness and death, but the delta variant is likely responsible for increased numbers of breakthrough infections -- breakthroughs that could be as infectious as unvaccinated cases," Dr. John Brownstein, an ABC News contributor, said. "This internal document highlights the challenge we all now face in combating the most transmissible variant of COVID so far."

There are now 225 positive COVID-19 cases at the Tokyo Olympics, according to a tally kept by Olympics organizers.

That is an increase of 27 cases since Thursday. 

Of those cases, three of them are athletes. Two were in the Olympic Village at the time of their positive case, and one was not.

After President Joe Biden called on states to offer $100 to those who get vaccinated, Gov. Tim Walz said Minnesota would do just that.

"Good idea, @POTUS," Walz tweeted Thursday evening, following the president's COVID-19 vaccine address. "Starting July 30, every Minnesotan who gets vaccinated will get $100! All you have to do is roll up your sleeves."

Under the new incentive program, Minnesotans ages 12 and up who receive their first dose between Friday and Aug. 15 will be eligible for a $100 Visa gift card.

President Joe Biden is urging local governments to offer $100 to those who get vaccinated with funding from the American Rescue Plan.

Biden will also announce Thursday that all federal government employees and outside contractors will be asked to "attest to their vaccination status," and those who aren’t vaccinated must social distance, get tested once or twice a week and wear a mask at work no matter where they live. This includes members of the Armed Forces and National Guard.

Biden's also set to announce that small and medium businesses will be reimbursed for giving employees paid leave to get their family members vaccinated.

-ABC News' Molly Nagle