He's not really in a position to say "don't take the vaccine." Except of course it would support his "supporters"!
Also, t's not a true vaccine. He always called it a "shot" before.
There is another "covid vaccine" I've heard about - can't see anything about mRNA in its preparation. Looks like the spike glycoprotein is created and mixed with an adjuvant prior to injection, but maybe a vaccinefag could help check it out. Even if it doesn't have mRNA it could still be a concern. Here is a link
https://www.novavax.com/covid-19-coronavirus-vaccine-candidate-updates