Honestly somebody has to speak for the elephant in the room sometimes. It doesn't have to be a lot but I've found the question "were they vaxed?" After an abrupt death is a fast track for awakening others.

Note, don't accuse them, just ask, perhaps follow up, "there's a lot of rumors about the vaccine causing heart issues I was just wondering if this could be an example."

And then Leave it. Leaaaave it. Stop talking about it immediately. Let that seed grow, it doesn't need you watching over it. You can't make the seed grow the seed grows when viable conditions present itself. All you can do is try to condition them in a helpful way so they are poised to grow.