COMBINATION VACCINES CONSISTING OF ACELLULAR PERTUSSIS VACCINES

Combination vaccines consisting of multiple vaccine antigens delivered in a single injection simplify vaccine administration. Combining mult iple antigens into one injection, however, presupposes that the admini stration of multiple vaccines in combination will not reduce the safet y and immunogenicity of the component vaccines. New generation vaccine s seek to combine many more antigens from multiple, different pathogen s, making them difficult to study in controlled, double blind, randomi zed clinical trials because of the number of study arms required for c omplete evaluation. Methods to simplify studies of combination vaccine s include building on the framework of earlier studies to calculate sa mple size and reduce the number of control arms, standardizing serolog ic assays and assessment of adverse reactions and determining serologi c correlates of protection to minimize the need for multiple efficacy studies and to facilitate evaluation of immunogenicity studies. Prelim inary data indicate that immune responses to combination vaccines incl uding diphtheria-tetanus-acellular pertussis, hepatitis B and inactiva ted poliovirus are comparable with those seen when the vaccines are ad ministered separately. In contrast studies of combination vaccines tha t include Haemophilus influenzae type b Hib antigens show a diminished Hib antibody response, although the clinical relevance of this lowere d antibody response has not yet been determined. Numerous small safety studies of combined vaccines have not found evidence of increased adv erse reactions.