it's not too late to get some medication from your doctor. (similar to those you take when you travel to less developed places) But I think I may need it for HK at my next trip...
1st thing you should do is to get the hepatitis A and B vaccine called Twinrix.
It's avail from local pharmacy and you must get it and bring it along to your family physician to inject.
I'd rather get all these injections done before the trip...knowing full well that Hep-B is a common infection from HK, mainland and various Asian countries.