https://news.yahoo.com/trump-dismisses-covid-19-booster-184022005.html
It sounds like Trump is now beginning to publicly cast some doubt on the vaccines. He's starting cautiously, by questioning the booster shots, but I suspect (hope) that he will be slowly ramping up the questioning and criticism going forward, from here on out.
Here you go. He was speaking about JnJ:
https://nypost.com/2021/04/19/trumps-urges-americans-to-get-vaccines-takes-shot-at-jj-pause/