This supplementary statement provides information on and recommendations for the use of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP). One such vaccine was recently licensed, ACEL-IMMUNE.* This vaccine is licensed for use only as the fourth and fifth doses of diphtheria, tetanus, and pertussis vaccination; it is not licensed for the initial three-dose series in infants and children, regardless of age. At least one other DTaP product is anticipated to be licensed in the future for use as the fourth and fifth doses. The current Immunization Practices Advisory Committee (ACIP) statement on diphtheria, tetanus, and pertussis issued August 8, 1991, gives general recommendations on pertussis prevention, including the use of whole-cell pertussis vaccines for primary and booster vaccination (1).