<p>I think the vaccine kinda works, hence Ravi only needs brains once a month or so and therefore may be "human" for those periods. Also, I seem to recall it being mentioned near the beginning of the season that Liv scratched him multiple times; I'm assuming that means he gets cured, perhaps? And then gets scratched again to see if it will prevent the infection completely, which it doesn't seem to do.
</p><p>It's a bit confusing.
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