IMMUNOGENICITY OF A 5-COMPONENT ACELLULAR PERTUSSIS-VACCINE IN INFANTS AND YOUNG-CHILDREN

Objective: To compare the reactogenicity and immunogenicity of an acellular vaccine containing pertussis toroid, filamentous hemagglutinin, and fimbriae 2 and 3, with and without the 69-kd membrane protein, alone or combined with diphtheria and tetanus toxoids. Participants and Setting: One hundred thirty-seven 17- to 18-month-old and 22 4- to 6-year-old children who had received three or four previous doses of whole-cell vaccine, respectively, were recruited from public health immunization clinics. Design and Interventions: Three groups of children were sequentially enrolled in the study to receive the acellular pertussis vaccine with or without a 69-kd protein (CP4 or CP5, 17- to 18-month-old children), the two vaccines combined with diphtheria and tetanus toxoids (CP4DT or CP5DT, 17- to 18-month-old children), or the CP5DT vaccine (4- to 6-year-old children). Children were assigned to the first two groups in a randomized and double-blind fashion; the last group was formed by open enrollment. Data regarding adverse reactions were recorded by the parents and collected via a structured interview administered seven times, five times during the first 72 hours. Serum samples were obtained before and 1 month after the immunization, and antibodies against each constituent of the vaccine were measured. Results: A systemic adverse reaction was reported in 40% to 65.7% of 17- to 18-month-old and 38.1% of 4- to 6-year-old children; no severe reactions occurred. A local reaction was reported in 8.6% to 29.4% and 71.4% of children, respectively. No differences were detected between vaccines; inclusion of the 69-kd membrane protein did not increase reactogenicity. All vaccines elicited an antibody response to all antigens contained in the formulation. Conclusions: The five-component acellular pertussis vaccine (Connaught Laboratories Ltd, Willowdale, Ontario) is safe and immunogenic in 17- to 18-month-old and 4- to 6-year-old children. The 69-kd protein was immunogenic, and its inclusion neither increased side effects associated with the vaccine nor adversely affected the antibody response to the other components.