One of the tropes of the anti-vaccine religion is that childhood diseases, like measles or whooping cough, are not dangerous. But real science tells us that measles complications, like SSPE (subacute sclerosing panencephalitis) and death, are not innocuous. The ignorance about measles puts our children at risk.
Generally, the popular assumption is that the infant immune system is weak, making those children more prone to viral or bacterial infections. The antivaccine crowd uses this belief to either state that vaccines won’t work or might actually harm the immune system, along with some overstated magical properties of human breast milk to prevent infection.