ABSTRACT. Selected metabolic, hematologic, and immunologic functions were evaluated in 3-to 6-mo-old Finish infants who received whole-cell pertussis-component diphtheria and tetanus toxoids and pertussis vaccine, adsorbed (DTP) vaccine, and in 4-to 6-y-old Los Angeles children who received either a licensed DTP va-ccine or an acellular pertussis component DTP vaccine. One d after immunization, there was an increase in total leukocytes and neutrophils and a decrease in lymphocytes in all vaccinees. In 4-to 6-y-old children the leukocytosis and neutrophilia were greater in recipients who received the standard DTP vaccine than in vaccinees who received an acellular pertussis component DTP vaccine. In infants there was an increase in the mean plasma insulin concentration but no change in the glucose concentration 24 h after immunization; no increase in the mean plasma insulin was noted in the 4-to 6-y-old children. Three 4-to 6-y-old vaccinees had higher circulating immune complex concentrations after immunization and two of these children had high clinical reaction scores. The etiology of adverse reactions after DTP immunization is multifactorial. In contrast with findings in animals, our findings do not demonstrate a clinically significant effect due to lymphocytosispromoting factor on glucose metabolism in vaccinated children. Neutrophilia in vaccinees is probably due to endotoxin, and some reactions may be due to circulating immune complexes. (Pediatu Res 27: 353-357,1990) Abbreviations AHG Eq, aggregated human gammaglobulin equivalent APDT, acellular pertussis component DTP vaccine CI, confidence interval CIC, circulating immune complexes DTP, diphtheria and tetanus toxoids and pertussis vaccine, adsorbed FHA, filamentous hemagglutinin LPF, lymphocytosis-promoting factor LPS, lipopolysaccharide WBC, white blood cell kocytosis with a predominant lymphocytosis, and marked adjuvancy in several immunologic systems (1-4). These effects are primarily due to the Bordetella pertussis antigen LPF but LPS (endotoxin) may also contribute to the metabolic, hematologic, and immunologic findings.Many adverse clinical events occur after pertussis immunization in children, but the pathophysiology of these events is not well understood (1,2, 5). It has been suggested that some of these adverse events may be due to biologically active LPF and LPS that are present in routinely used DTP vaccines. There are, however, few data available that indicate that these antigens are in sufficient concentration in presently used DTP vaccines to produce hematologic or metabolic changes in vaccinated children.In Japan, acellular pertussis vaccines have been used for the routine immunization of children since 198 1 (6-8). These vaccines contain significantly reduced amounts of LPS and biologically active LPF, and their use has been associated with fewer vaccination side effects than occur in whole-cell pertussis vaccine recipients. Because of the paucity of information relating to hematologic and metabolic effects and immune complex formatio...