I don't have any idea on why they'd tell you not to shower for 8 hours. That just seems kind of stupid. But, the alcohol part makes some sense because booze can have a negative effect on your immune system where it doesn't react as strongly to the vaccine. Plus, you know, getting headaches or being hung over from drinking probably isn't great when you already feel like shit.

I think the only thing they told me when I had my vaccines were to just not do any strenuous activity for the following 48 hours. If only they had told me not to shower for a week so I could have cosplayed trying to be a farm pig. Oh well.