Microbes that elude host's defenses and have developed resistance to the existing antibiotic arsenal continuously invade the human body. Cure for such diseases is inevitable as it may result in high morbidity and mortality, if not properly treated. Vaccination represents the most cost-effective way for disease prevention. Vaccines activate sentinels of the immune system including macrophages and T, B, and dendritic cells to release a battery of effector molecules and cytokines and ward off infection. For long-lasting protection, the memory cells also need to be evoked. This book encompasses biotechnological vaccines in clinical use, cocooning, disease resurgence postvaccination and other vaccine adverse effects, prospects of therapeutic versus prophylactic vaccines, and design of effective vaccines using bioinformatic tools and engineering molecular pattern interactions.