See beer can save live. Cheer lads!!!

Yeah, from what I can tell it was the act of boiling water that helped prevent various illnesses-- NOT the beer itself (though they did not understand this at the time), and NOT the plague. There was a myth/tale/rumour that his church survived the plague due to drinking beer, but considering that's not how plague is spread (as far as I know), this is most likely just a big fish story. Either they did survive and it was a coincidence, or they didn't all survive.

More likely typhoid, which would be reason enough to drink beer!

From what I've heard the realization that it was safer than water was a large part of beer initially gaining popularity.