A. Vaccines are given at an early age because the diseases they prevent can strike at an early age. Some diseases are far more serious or common among infants or young children.

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.

The ages at which vaccines are recommended are not arbitrary. They are chosen to give children the earliest and best protection against disease.

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