Disbelief in science in general has a massive impact - causing deaths.
Even disbelief in evolution causes deaths, e.g. if we don't do enough to deal with antibiotic resistance.
I wonder if this is true? What is correlation of Americans who "don't believe in evolution" who would reject the notion of antibiotic resistance in infectious diseases if you explained it to them? I wonder how many would reject the notions of husbandry, e.g. if you continually breed for a certain trait, like agreeableness, that the offspring will be on average more agreeable than the previous generation.
There is the religion of Christian Science, which rejects taking all medicine, but even there, that would only seem to be beneficial in antibiotic preservation practices.