It doesn't matter. This is old news, all shingles vaccines have this effect, as well as flu vaccines and other late age vaccines. The point is, over 60, you want to avoid any strong viral infection. And it's not just dementia, also protects from Parkinson and ALS. These viral responses trigger a huge load of reactive oxygen levels that an older brain cannot handle because of reduced mitochondrial efficiency from aging.

The difference is becoming more apparent in recent years because we now have a large control group of vaccine avoiders that voluntarily decided to be the control group that otherwise would have been ethically impossible. Post 2020 "doing my own research" will see a surge in these neurodegenerative diseases in 20 years.

Antivaxers, thank you for your service.

Saw a comment about it being an older vaccine and nothing else. Here is the reddit link to the same story, if you want a little more info.