Does varicella (chickenpox) vaccine attenuate over time? I had one dose of vaccine when I was an infant almost 20 years ago, but for some reason I never got a second dose (I went through all of my records to confirm this). I've never had the actual pox, either. Can I just get one booster dose and be done with it, or has too much time lapsed, and I need a new series of two shots? Can any virologists give me a quick rundown?