Two hundred thirty-four infants were randomly assigned to receive either DTaP-MA, DTaP-Conn, or DTP-MA vaccine by intramuscular injection in the anterolateral thigh at 2,4, and 6 months of age. DTaP-MA vaccine contained 25μg of tetranitromethane inactivated pertussis toxoid (PT) and 3 μg of formalin inactivated filamentous hemagglutinin (FHA); DTaP-Conn contained 25μg each of formaldehyde inactivated PT and FHA. Study personnel were blinded only to the Mass DTaP and DTP vaccines. Subjects received a Hib conjugate vaccine (Mass Hib-T) in the opposite thigh during the same visits. Local reactions (any injection site redness, swelling, pain/tenderness) and systemic symptoms (sleepiness, fussiness, crying more than usual, persistent crying, vomiting, eating less than usual) were monitored for up to 72 hours following each immunization. Analyses used Chi-square or Fisher's Exact test. Serum was obtained one month after the third immunization for measurements of antibody to PT by direct IgG class ELISA and by CHO cell neutralization and to FHA by direct IgG class ELISA. There were no differences in local reactions after each dose, except between DTaP-Conn and DTP-MA at 4 months (p=.001). The same can be said for systemic symptoms except between each DTaP and DTP-MA at 2 months (p<.01). Geometric mean titers (GM in μg/ml) for PT and FHA were significantly greater after DTaP-Conn than DTaP-MA (p<.05) as shown below: Table When given as the primary series to infants at 2,4, and 6 months of age, these acellular vaccines induced fewer systemic symptoms in 2 month old infants compared with DTP-MA and both DTaPs induced antibodies to PT and FHA. (Funded by Univ. of MA Biological Laboratories)