Like other people, he has become a victim of conspiracy theorists. We had a thread headed by someone else in your position - except it was a sister, or a relation like that.
I suspect that the only thing you can do, is just refuse to discuss the subject with him other than tell hin, you will decide for yourself when the opportunity for a vaccine presents itself.
Govt announces Ukrainian style scheme to bring thousands more migrants to UK
Venezuela earthquakes, is £2million all the UK can afford to send for the relief effort?
Doctors and how they come across
and to also think that governments around the world want to tank their individual economies, defies logic!