Dr. Anthony Fauci, the White House's chief medical adviser, said on Monday that former President Donald Trump had been "poisoning the well" against vaccines for a long time prior to his recent public support of the jab.
Fauci said he was glad that Trump supported vaccines, but that the former president's mixed signals about the shots contributed to vaccine hesitancy among Americans.
Fauci told CNN's Kaitlan Collins that "Poisoning the well early on about not being enthusiastic or pushing vaccines, discouraging vaccines, now has a residual effect."
Fauci was Trump's medical adviser during the latter's presidency and described their working relationship as " somewhat awkward" because the two appeared to continually contradict each other.
The crowd booed when Trump said he had already taken his booster shot and voiced his support for the vaccines.
Fauci said that some of the people who have been following his every word are now pushing back and not listening.
Fauci told Collins that he was stunned by the fact that he was doing that, and that he was getting booed in some places.
The strength of the divisiveness in our society is the biggest stumbling block to getting the Pandemic under control, he said.
He told Collins that it is not a place for divisiveness when there is a classical, historical, unprecedented pandemic. It doesn't make sense.
The development of the shots was called one of the greatest achievements of mankind by Trump in an interview with right-wing pundit Candace Owens last week.
Fauci said he hopes the former president will keep up the good work.
President Joe Biden's administration has pushed for vaccine mandates this year, despite Trump's opposition.
More than 200 million Americans above the age of 5 have been fully vaccined, and more than 200 million Americans have received at least one vaccine, according to official data.