Vaccines, used appropriately and efficiently, have changed the landscape of infectious diseases. Poliomyelitis is almost completely eliminated globally. In many industrialised countries, there has been over 99 percent reduction in incidence of diphtheria, tetanus, measles, mumps, rubella, Haemophilus in-fluenzae b meningitis and over 97 percent reduction in whooping cough.',2Unlike anti-biotics, most vaccines have remained equally effective despite years of continuous usage.