Is the protection from vaccines complete and how long does the protection last?


No vaccine offers 100% protection. Also, children have several types of immunity. Therefore this has to do with individual responses to vaccines - the duration will depend on the vaccine type, the child's immunity and response to the vaccine. This makes it difficult for researchers to predict or measure the length of time you child is protected after immunization. At the outset, about 90% of efficacy is offered and with time some of the immunity is lost. However, most vaccines offer protection during the time period when the child is most at risk. Also, should the child contract the illness despite immunization, the vaccine will work at lessening the intensity of the disease, even if it doesn't provide total protection. Measles and hepatitis B vaccines are known to create lifelong immunity in a lot of people. But some vaccines need boosters throughout life to remain preventive. Examples include pertussis vaccine and the vaccine for tetanus which does not produce lifelong immunity, therefore requiring booster dose during adolescence. Vaccines against the flu virus provide short-lived immunity plus the virus mutates on a yearly basis. Thus vaccines have to be created according to the strains of flu and the doses are given year after year.

Chickenpox is a good example of a disease in which repeated exposures may actually boost the immune system. Varicella vaccines are given to young children thus providing immunity against the virus and when they are exposed to someone with the disease later on, they are less likely to suffer from the disease but instead receive a boost to the immune system.