Q: I have given all the vaccines (compulsory as well as optional) to my 20 months old son. Can he still get infected by chicken pox, meningitis or such fatal diseases at any stage of life or he is completely safe for the rest of his life?

A:There is nothing known as absolute safety for the rest of the life with vaccination. However, there is a very high probability over 95% for most diseases vaccinated for and over 85% for others that the child will not get these diseases. It is now becoming clear that the immunity decreases over several years (decades) and revaccination may be required for some of these diseases during adolescence or adulthood or even earlier. For example, to keep immunity for tetanus functional, a booster vaccination is needed every five years.