The United States has made tremendous progress in using vaccines to prevent serious, often infectious, diseases. But concerns about such issues as vaccines' safety and the increasing complexity of immunization schedules have fostered doubts about the necessity of vaccinations. We investigated parents' confidence in childhood vaccines by reviewing recent survey data. We found that most parents-even those whose children receive all of the recommended vaccines-have questions, concerns, or misperceptions about them. We suggest ways to give parents the information they need and to keep the US national vaccination program a success.

ABSTRACT. Recent surveys found that an increasing number of parents are concerned that infants receive too many vaccines. Implicit in this concern is that the infant's immune system is inadequately developed to handle vaccines safely or that multiple vaccines may overwhelm the immune system. In this review, we will examine the following: 1) the ontogeny of the active immune response and the ability of neonates and young infants to respond to vaccines; 2) the theoretic capacity of an infant's immune system; 3) data that demonstrate that mild or moderate illness does not interfere with an infant's ability to generate protective immune responses to vaccines; 4) how infants respond to vaccines given in combination compared with the same vaccines given separately; 5) data showing that vaccinated children are not more likely to develop infections with other pathogens than unvaccinated children; and 6) the fact that infants actually encounter fewer antigens in vaccines today than they did 40 or 100 years ago. Pediatrics 2002;109:124 -129; multiple vaccines, immunity, parental concerns.

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