Why are vaccines given at a certain age?
Vaccines are given at an early age because the diseases they prevent can strike at an early age. For example, up to 60 percent of severe disease caused by Haemophilus influenzae type B occurs in children under 12 months of age. Infants less than 6 months of age are at highest risk for serious complications of pertussis — 72 percent of children under 6 months who get pertussis must be hospitalized, and 84 percent of all deaths from pertussis are among children under 6 months. Also, some vaccines work best when they are given at certain ages. For example, measles vaccine is not usually given until a child is at least a year old. If it is given earlier than that, it may not work as well.
