Vaccination has been one of the great successes of 20th century medicine. The next century promises to continue that “golden age” through the use of new strategies made possible by the genetic manipulation of microorganisms. In particular, vectors that carry genes coding for important antigens, recombinants that produce proteins, reassortants containing mixtures ofgenes, and agents deleted for particular genes will be used for the purpose of vaccination. The author discusses the specific needs for new vaccines and speculates on the routine schedule of immunization in the next century.