Dose-response to a two-component acellular pertussis vaccine in infants and comparison with whole-cell vaccine

in an effort to determine the optimal dose of pertussis toroid (PT) and filamentous haemagglutinin (FHA) for use in a cellular pertussis vaccines we compared the immunogenicity and safety of acellular pertussis vaccine combined with diphtheria and tetanus toxoids containing 12.5 mu g (DTaP-12.5) or 25 mu g (DTaP-25) each of PT and FHA with a whole-cell pertussis vaccine in infants immunized at 2, 4 and 6 months of age. Recipients of acellular vaccines developed higher anti-FHA concentrations and more rapid anti-PT serological responses than infants who received whole-cell pertussis vaccine combined with diphtheria and tetanus toxoids (DTP). A dose response was noted; infants immunized with DTaP-25 developed significantly (P < 0.03) higher anti-FHA and anti-PT levels than infants who received DTaP-12.5. No rise in agglutinin titres was noted for recipients of the acellular vaccines although this vaccine stimulated increases in agglutinins when given as the fourth or fifth dose to children who had received three doses of DTP. The rates of erythema, induration, pain, irritability, crying, increased sleepiness,and decreased appetite were significantly (P less than or equal to 0.05) lower in infants who received a cellular vaccines than in infants who received DTP. When the data from injections at 2, 4 and 6 months of age were combined, no significant differences in the rates of any adverse event were noted for recipients of DTaP-12.5 Sor DTaP-25. The rates of most adverse reactions following DTP decreased from the first to the third immunization except fever, which increased. For a cellular vaccine recipients, the rates of fever and erythema increased somewhat from the first to the third injection but remained far below the rates following DTP. The acellular vaccine was safe and immunogenic, and a dose-response effect was demonstrated. (C) 1998 The International Association of Biological Standardization.