Vaccines remain one of the most successful and scientifically validated public health interventions, yet public understanding often lags behind rapid advances in immunology and platform engineering. Drawing on four decades at the bench, Prof. Madhubala traces the history of vaccination from Jenner to the mRNA era. This lecture will provide a clear, mechanistic overview of how the immune system detects pathogens, forms long-lasting memory, and how modern vaccine platforms, including whole-virus, protein-subunit, viral-vector, and mRNA technologies, are designed to engage these pathways with precision. The talk builds from basic immunology through vaccine platforms, adjuvants, and the clinical-trial pipeline; it then goes deeper into molecular and systems immunology: innate sensing, antigen presentation, germinal-center maturation, and nanoparticle delivery systems, structure-based antigen design, and reverse vaccinology, illustrated through HPV, COVID-19, influenza, malaria, and the speaker's own indigenous leishmaniasis vaccine platforms. The lecture will also address the scientific basis of vaccine hesitancy, connecting foundational biology with translational challenges to offer students, researchers, and practitioners a comprehensive understanding of how contemporary vaccinology integrates molecular science, engineering, and public trust. Throughout, connections are drawn to chemistry, molecular recognition, reaction kinetics, and formulation science, showing vaccinology as applied molecular science. The lecture closes on the field's emerging frontiers and its central remaining challenge, which is no longer purely scientific but translational: getting safe, effective vaccines to everyone who needs them, and ensuring they trust what they receive.