The speed of the vaccination programme has been blasted by the likes of Senator Mitt Romney, who called the rate of distribution “inexcusable.”
“I’m telling you that things are changing. 1.5 million doses in the last 72 hours. That’s meaningful change,” Dr Adams told CNN’s Jake Tapper.
“There’s what we delivered, and we hoped that would translate into vaccinations, that has not occurred to the way that we would like.”
The White House had claimed that 20 million people would receive the vaccine before the end of 2020.
But the Centres for Disease Control said that as of Saturday just 4.2 million injections had been carried out.
An estimated 20.5 million Americans have so far tested positive for coronavirus and more than 350,000 have died from it during the pandemic.
Dr Adams also refused to defend Donald Trump’s claims on Sunday that the Covid death figures have been “far exaggerated.”
“From a health perspective, I have no reason to doubt those numbers,” added Dr Adams.
“I don’t speak for the president.
“I speak for the office of the Surgeon General and the Public Health Service, and I’m focused on making sure people get the information they need and wash your hands and stay your distance and get the vaccine when it’s available.”
Earlier Dr Anthony Fauci had disagreed strongly with Mr Trump.
“There’s no running away from the numbers,” he said on ABC’s This Week.