Rabies vaccines

http://www.straightdope.com/mailbag/mrabies.html#update

The above rabies column didn’t answer the question: Why is the dog vaccine so much cheaper than the human? They’re both rabies antigens, right?

Are they prepared differently? Are there different safety standards? It’s incredibly frustrating when Cecil himself doesn’t answer the question…

Why would dogs need to be vacinnated against people???

Moving this to the forum on Mailbag answers.