Both sides in Europe didn't use Chem/Bio weapons because of the threat of mutual retaliation.
Japan refused to use them on the US because of the same. (can't be said about them an China).
I don't think they would have been eager to use them, and by the time they were desperate enough to try delivery would have been highly difficult if not impossible. (and I discount use of missiles as delivery systems because of the limited payload of the V2 at the time.)
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