Background The European Advisory Board on Cat Diseases (ABCD) is a body of experts that sees its task as bringing feline health issues to the forefront of companion animal practice. By way of an introduction to this special ‘clinical practice’ issue of the Journal of Feline Medicine and Surgery (JFMS), this article attempts a ‘helicopter view’ of practical, or applied, immunology. It should be viewed as a ‘light primer’ to vaccines and vaccination, and is very general in nature. It is not intended to replace authoritive immunology textbooks, which abound both in the veterinary and medical fields, and the level of detail in which may discourage the casual reader. By design, therefore, this article is not referenced. Underpinning issues) immunity, and the types of vaccine developed and/or available (live, killed, chimaeric, DNA-only products). Practical relevance With day-to-day veterinary practice in mind, practical issues discussed include kitten vaccination, the definition of ‘core’ versus ‘non-core’ products, passive immunisation, and prevention strategies in populations and crowded cat communities. Adverse reactions, and factors affecting vaccine efficacy, safety and performance are also summarised.