TUDIES of immune response to the individual components of a multiple vaccine containing polionmyelitis antigens combined with the widely used triple combination of diphtheria and tetanus toxoids and pertussis vaccine (DTP-Polio) soon followed the demonstration of the effectiveness of poliomyelitis vaccine in the 1954 field trial (1, 2). Results of experiments in guinea pigs and monkeys (3) encouraged Brown and Kendrick (4) to study this multiple preparation in children. In general, they obtained good response to the individual antigens; they noted particularly the suppressive effect of maternal antib,ody on the infant's response, especially to the poliomyelitis components. Meanwhile, Batson and associates (5) reported satisfactory response of infants to poliomyelitis vaccine when it was mixed with DTP in a syringe immediately before injection. Schuchardt and associates (6) obtained a good response in monkeys to the individual components of DTP-Polio; they found some indication of an increased response to poliomyelitis antigen with the combined preparation. Wilson and associates (7) studied a group of infants in Canada, most of whom were und'er 5 months of age at the time a primary course of quadruple vaccine was initiated, with a recall dose 1 year later. Most of the infants responded well to all three types of poliovirus and in all but one of those who failed to respond, the initial level of maternal antibody was high. Diphtheria and tetanus antitoxin titers were also measured and found satisfactory. In several studies of DTP-Polio, Barrett and associates (8-10) analyzed their findings in detail. In their last report (10) these authors studied particularly the age factor in the response of infants 1 day old to 7 months of age at the start of immunization, but considered that four injections with combined antigen at monthly intervals overcame such interference encountered in infants started as early as 3 months of age. Even with four injections, a booster dose after about 6 months was considered important for reinforcing basic immunity. The possible relationship of a DTP-Polio vaccine to the development of an efficient immunization procedure in young infants has stimulated recent studies by a number of other authors (11-18), some of them being specifically Dr. Brown is professor of epidemiology and Dr. Kendrick is resident lecturer emeritus in epidemiology, School of Public Health, University of Michigan, Ann Arbor. Dr. Volk is commissioner, Saginaw County Department of Health, Saginaw, Mich. Dr. Gottshall is chief of the antigens and antisera unit, biologics products section, and Dr. Anderson is chief of the biologics products section, division of laboratories, Michigan Department of Health, Lansing. The authors are members of the Technical Committee on Immunization of the American Public Health Association, under whose spoinsorship and guidance this study was conducted. The study was supported by grants from the National Foundation and the Public Health Service, E-2412 (C2) Al SS. This paper was presented at the meeting of the A4merican Public Health Association, November 13, 1963, at Kansas City, Mo.