So it turns out that research is now showing that an oral flu vaccine may be more effective due to the mode of transmission being the same as real flu infection - "sublingual" or under the tongue vaccination. (Well BBC, anyone in H and V could have guessed that - we should so be teaching this stuff by now :) ) Anyway, BBC also says that vaccinating up the nose is dangerous because it can travel to the CNS. However, sublingual vaccinations do not hold this risk.
Okay so here ya go Nick, this is for you...
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