I have reached the age that I know it's better not to argue with anyone on anything unless I have an interest in. Life is too short for meaningless arguments. Arguing with family members has the additional "bonus" that you are gonna to break down some long term close relationship.
I have an interest in my dad not dying, however remote the chance might be, from a preventable disease. However, his anti-covid-vaccine stance makes him a danger to himself and others from this imminent threat.