Participants and Setting
One hundred thirty-seven 17- to 18-month-old and 224- 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.

(Arch Pediatr Adolesc Med. 1994;148:495-502)