The
haemophilus vaccines are made of the type b capsular
polysaccharide of haemophilus influenzae, polyribosylribitol
phosphate (PRP), which is responsive of pathogenic power. However the responsiveness of children to PRP
vaccine was found to be very poor in infants. The concept of conjugating
carbohydrate with a
carrier protein increasing immunogenicity of the PRP led to 4 PRP--
protein conjugate vaccines: PRP-
diphtheria toxoid conjugated
vaccine (
PRP-D), outer-
membrane protein of Neisseria meningitidis conjugated (PRP-OMP), cross-reacting mutant
diphtheria protein (PRP-HbOC) and
tetanus-Toxoid conjugated
vaccine (
PRP-T). The antibody response to PRP is enhanced and a good booster response is obtained in infants as soon as two months of age. However the 4
vaccines differ markedly in ability to stimulate antibody production.
PRP-D is less immunogenic and must be given in children older than 12 months.
Antibodies are significantly higher after 3
injections of
PRP-T or PRC-HbOC than PRP-OMP. Only PRP-OMP produces a clinically pertinent elevation of
antibodies after 2
injections. The coadministration of PRP-OMP, PRP HbOC,
PRP-T with
diphtheria-
tetanus-
pertussis vaccines does not alter the antibody PRP response. The
polio antibodies are lower if
injectable polio vaccine is mixed with PRP-OMP, but the level is the same with
PRP-T vaccine. The others
antibodies (D, T, Coq), are at same levels. The field trials have shown a high efficacy of all those 4
vaccines. However
PRP-D vaccine gave less good result in infants before 6 months. The safety of these
vaccines is good and not altered by combination with investigation by
diphtheria-
tetanus-
pertussis vaccines.(ABSTRACT TRUNCATED AT 250 WORDS)