Cousin Refusing To Vaccinate Her Children

My young cousin, who has 2 very young children, recently yelled at me when I suggested that she get her kids vaccinated. She said that the vaccines give people cancer (despite both her and me having received them when we were her kids' ages). How do you deal with people like this? Honestly, I worry about my cousin's kids: I told my cousin that the vaccines help in preventing serious illness when a disease is contracted and also helps to prevent the immune system from being seriously damaged because of them illnesses and she still insisted that she wouldn't give her daughters the vaccines because she didn't want them to get cancer.