Comment by native_samples

That supports my point, no? The paragraph you cited boils down to "there is an association between being less sick and not getting Alzheimer's (i.e. being less sick" + "there seems to be an association between literally any vaccine regardless of mechanism or target and less Alzheimers". These are not specific biological mechanisms of action, they're just correlations supported by an ultra-vague causal hypothesis of the form "maybe microbes cause Alzheimers". That's not actually a causal biological explanation.