President Joe Biden's administration continues its ambitious vaccine rollout in the face of the pandemic that's killed over 500 thousand Americans.

A key part of this is convincing the public that the vaccine is safe to take and vital for slowing the spread of the virus that's upended daily life for more than a year. As a component of this effort, every single living President has publicly taken the vaccine and appeared in public service announcements urging Americans to follow suit—all but one, that is.

News broke earlier this month that former President Donald Trump and then-First Lady Melania Trump took the vaccine in secret, and while Trump has credited himself with its rollout, he has yet to urge his supporters to take it.

White House press secretary Jen Psaki was asked about this in a Monday briefing.

Watch below.

The White House press secretary said:

"If former President Trump wanted to be more vocal about the safety and efficacy of...the vaccine, certainly we'd support that. ... Every other living former President, or most of them if not all of them, has participated in public campaigns. They did not need an engraved invitation to do so."

Psaki also emphasized that most Republicans indicated they would trust the vaccine if their doctors or healthcare providers recommended it to them, noting that this was "an important place to invest."

Psaki's comments come after Biden's leading health advisor, Dr. Anthony Fauci, publicly urged Trump to tell his supporters that the vaccine is safe. His comments were in response to news that nearly half of Trump supporters don't intend to take the vaccine.

Many of Trump's critics took his silence as a further indictment of his ego.

But they applauded Psaki for calling him out.

The Biden administration is currently set to outpace its goal of 100 million vaccine doses in 100 days.