White House COVID-19 coordinator Dr. Ashish Jha issued a dire warning Thursday that the U.S. will be increasingly vulnerable to the coronavirus this fall and winter if Congress doesn't swiftly approve new funding for more vaccines and treatments.

In an Associated Press interview, Jha said Americans' immune protection from the virus is waning, the virus is adapting to be more contagious and booster doses for most people will be necessary — with the potential for enhanced protection from a new generation of shots.

His warning comes as the White House says there could be up to 100 million infections from the virus later this year — and as President Joe Biden somberly orders flags to half-staff to mark 1 million deaths.

"As we get to the fall, we are all going to have a lot more vulnerability to a virus that has a lot more immune escape than even it does today and certainly than it did six months ago,” Jha said. "That leaves a lot of us vulnerable.”

Jha predicted that the next generation of vaccines, which are likely to be targeted at the currently prevailing omicron strain, “are going to provide a much, much higher degree of protection against the virus that we will encounter in the fall and winter." But he warned that the U.S. is at risk of losing its place in line to other countries if Congress doesn't act in the next several weeks.