Elsewhere in this issue of The Journal (p 533), Warren and his associates present data suggesting that the combination of killed measles and poliovirus antigens in a single vaccine is capable of evoking antibodies against all four components (measles, poliovirus types 1, 2, and 3) in most susceptible vaccines. Their findings prompt comment on the timing of immunization as well as focusing attention upon the technical problems of combined vaccines.
The ultimate purpose of immunization in early infancy is to protect a population which is at high risk. Case-fatality rates for most of the severe childhood diseases are higher in the first year of life than later. For example, almost three fourths of all deaths due to pertussis in 1955 occurred during the first year of life. Similarly, measles morbidity and mortality is higher in infancy than in childhood. For these reasons, it is desirable to administer effective vaccines as