The immunogenicity of an acellular pertussis vaccine containing genetically detoxified pertussis toxin, filamentous haemoagglutinin and pertactin was studied in 12 children [median age, 45 (6-107) months] with perinatal human immunodeficiency virus-type I (HIV-I) infection, Antibody response to all antigens was observed in six cases and another children 3 reacted to two or one antigen(s), but titres were lower than those from healthy controls, Antibody title fold-rise correlated with preimmunization CD4-positive cell counts, Significant titles were still detectable 4 months after the third nose, The acellular vaccine is immunogenic in a portion of children with perinatal HIV-I infection but early vaccination might be mole effective, taking advantage of still adequate CD4-positive cell numbers. (C) 1997 Elsevier Science Ltd.