And as a consumer of medicine, I observe that doctors are equally confident when they really don't know what they're talking about, and when their opinions aren't substantiated by science. (The command to wear padded running shoes, for instance.)
And I know that the CIA organized a fake "vaccination drive" to get Osama bin Laden.
So I understand why people who might not have a scientific education choose not to believe the vaccination story they're given by their government.
Saying it louder and more often won't help.