I was worried about the wearing off too. I asked my GP about this (he is a GP I trust). He said that they are constanty researching this and that for those that are wearing off after a set number of years (eg 10), they are setting up for re-immunisation as teenagers. I also asked whether he needed ones like chicken pox and the GP recommended yes, as he said there are some serious complications that can occur with chickenpox (can't remember which ones, but he listed a few). I ended up deciding to do them all. My personal choice and I don't criticise others.