A cocoon vaccination strategy refers to vaccinations in persons from the immediate environment of those patients who might develop an illness (they are susceptible to illnesses) but cannot be vaccinated due to permanent or temporary medical contraindications to a vaccination (e.g. immunosuppressed patients) or are too young to have a vaccination. Most frequently, a cocoon vaccination strategy is associated with vaccinations in adults aimed at preventing the spread of an illness in children (e.g. pertussis vaccination or inluenza vaccination), but it is worth considering whether this strategy should not be understood also as vaccinations in children with the view of protecting adults and the elderly against illnesses (e.g. inluenza or pneumococcal diseases). The aim of the cocoon strategy is to minimize the risk of the transmission of pathogens in the environment of a patient who is susceptible to an infection. A vaccinated patient is not a source of infection any more for a non-vaccinated patient. The chapter presents a history, current implementation of the strategy in diferent countries, its beneits and limitations.