According to three people familiar with the matter, then-President Trump was repeatedly warned by some of his closest advisers and administration officials about this MAGA-specific issue during his closing weeks as leader of the free world. But in the two months since President Joe Biden took over at the White House, polls show that aversion to the new coronavirus vaccines remains markedly higher among Trump fans and GOP voters than it is among liberals and Biden supporters. That reality has stoked grave concern among public health officials and experts, and has left some of the ex-president’s friends and allies frustrated over the fact that Trump, from his new home in Florida, isn’t doing more to reach his base and combat the problem.

“I have practically begged him to get out there constantly [during his post-presidency] and make videos calling on his supporters who are hesitant to get their shots,” one person close to Trump said. “Last time I checked in, I hadn’t heard of any positive movement in that direction.”

In a small number of public appearances and TV interviews lately, the former president has encouraged—at times as mere asides—his true believers to get vaccinated, but has yet to embark on anything close to a vigorous campaign to leverage his sizable megaphone on the subject. Further, it was not publicly revealed he and then-first lady Melania Trump had been vaccinated until nearly a month and a half after he was no longer president.