Board Thread:General Discussion/@comment-6192846-20130913170916/@comment-24463571-20140612145220

I'm not entirely sure putting the words "vaccine" in katakana is necessarily a sign of emphasis, as it's actually very common for the word to be written in katakana.

It would make the most sense, at least to me, if the baby had a very low dosage of the Golden Key's powers (perhaps from its father), thus making it a "vaccine". It still seems not very effective. Vaccinating an already sick person does absolutely nothing. Unless the baby also had weakened jis tiama from Carlos, I can't see how it would be a vaccine. But with a demon, most likely anything can go.