The increasing number of useful vaccines for infants and children just
ifies the development of new combined vaccines. New methodologies are
needed for evaluation of efficacy, especially for acellular pertussis
vaccines. Such evaluation requires the use of previous immunogenicity
studies as a means to seek immune interference that might lead to decr
eased efficacy. Finally, definitive efficacy could be assessed by long
-term postmarketing epidemiologic surveillance. Different combinations
are discussed in relation to age of recipients (infants, children) ad
olescents, and adults) and national or regional epidemiologies.