Clinical, metabolic, and antibody responses of adult volunteers to an investigational vaccine composed of pertussis toxin inactivated by hydrogen peroxide

A toxoid vaccine, composed of purified pertussis toxin inactivated with H₂O₂ (NICHD-Ptxd), was developed on the basis of evidence that serum neutralizing antibodies (antitoxin) would confer immunity to pertussis. In vivo and in vitro assays of NICHD-Ptxd showed only trace or nondetectable levels of pyrogenic, adenosine diphosphate-ribosyltransferase, binding and pharmacologic activities. Nevertheless, about 40% of the antigencicity of pertussis toxin was retained. Adult volunteers were injected, two times 6 weeks apart, with either 10 (n=21), 50 (n=25), or 75 (n=30) μg/dose of one lot, Ptx-06, adsorbed onto Al(OH)₃. Neither fever nor changes in the levels of leukocytes, lymphocytes, fasting blood glucose, or insulin were observed in the volunteers. The optimal immunizing dose, 50 μg, induced levels of antitoxin (geometric mean (GM) 302 U) comparable to those found in eight adults convalescent from pertussis (GM 269 U) and greater than those found in 18-month-old children after their fourth dose of diphtheria and fetanus toxoids and pertussis vaccine (GM 20.0 U, p<0.001). These data indicate that NICHD-Ptxd is safe and immunogenic in adults, and they justify its evaluation in infants and children.