I'm about to do some travelling to Russia so I am getting all of my vaccines updated. The only two vaccines that I am not sure about are Hepatitis A & B. I had these vaccines before I did some travelling in 1997. WebMD's web-site says that Hep. A vaccines are supposed to last 20 years. Does that sound right? Immunize.org says that the Hep. B. vaccine is supposed to last 25 years. Does that sound right?