tion:Vaccine-preventable diseases and vaccines 6.1 General considerations VACCINATION is the administration of agent-specific, but relatively harmless, antigenic components that in vaccinated individuals can induce protective immunity against the corresponding infectious agent. In practice, the terms “vaccination” and “immunization” are often used interchangeably. 6.1.1 Disease prevention Vaccination is a highly effective method of preventing certain infectious diseases. Vaccines are generally very safe, and serious adverse reactions are uncommon. Routine immunization programmes protect most of the world’s children from a number of infectious diseases that previously caused millions of deaths each year. For travellers, vaccination offers the POSSIBILITY of avoiding some infectious diseases that may be encountered abroad. However, satisfactory vaccines have not yet been developed against several of the most life-threatening conditions. 6.1.2 Vaccination and other precautions Despite their success in preventing disease, vaccines rarely protect 100% of the recipients. No vaccinees, including travellers, should assume that there is no risk of contracting the disease(s) against which they have been vaccinated. For example, vaccination is not a substitute for avoiding potentially contaminated food and water. Consequently all additional precautions against infection should be carefully considered. 6.1.3 Planning before travel Before DEPARTURE, travellers should be advised about the risk of disease in the country or countries they plan to visit and the STEPS to be taken to prevent illness. No single vaccination schedule suits all travellers. Each vaccination schedule must be personalized according to the traveller’s previous immunizations, health status and risk factors, the countries to be visited, the type and duration of travel, and the amount of time available before departure. A medical consultation before departure is a good opportunity for the health-care provider to review routine immunizations and update them in addition to providing the travel immunizations indicated for the specific itinerary. Following vaccination, the immune response of the vaccinated person varies according to the type of vaccine, the number of doses administered, and whether the person has been vaccinated previously against the same disease. For this reason, travellers are advised to consult a travel MEDICINE practitioner or physician 4–8 weeks before departure in order to allow sufficient time for optimal immunization schedules to be completed.