People who believe in these types of theories usually want to feel part of a club or may just be gullible. Pulling up charts and figures likely will not help as they often dismiss it or change the theory. Listening to them and asking them why they feel that way and where they got the information can cause them to critically think about it and start to form the cracks in the theory. If you think you’re getting somewhere, maybe ask why vaccines and not another, more accessible form of medicine.

In this case, it sounds like the family doctor may be the source. Clarify exactly what this doctor said and what they would prescribe instead of a vaccine. It may be something homeopathic or a scam, or something else indicating the doctor is spreading a vaccine lie for their own gain.

If you’re getting nowhere, consider if this family member has a history of mental illness. Some disorders make people prone to skepticism and a general mistrust of the world, or cause magical thinking. Schizophrenia, bipolar (manic episodes), and OCD can sometimes be hard to spot.

Unfortunately, it could also be something ego-centered, and being “in” on a theory forms a core part of their identity, separating them from the “sheep”. They could be unempathetic to the idea of their actions spreading disease, or annoyed at the idea they have to take action to protect themselves. Based on the number of emotional responses in this thread and the general advice to block them or call them names, this is, sadly, a very likely cause. In this case, the best thing you can do is protect yourself by getting the vaccine that they won’t and limit physical contact. It’s a very sad reality that this line of selfish thinking has become extremely prevalent since COVID. I also had a vaccine skeptic family member who only gave it up once they caught COVID. They were lucky; take a look at r/DarwinAward to see the damage vaccine denialism causes.

Stay safe OP. I hope there is light for your family member.