Future combined vaccines.

The increasing number of useful vaccines for infants and children justifies 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 decreased 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, adolescents, and adults) and national or regional epidemiologies.