• Vaccine Name: H. influenzae Type b Capsular Polysaccharide Vaccine
• Target Pathogen: Haemophilus influenzae
• Target Disease: Meningitis
• Vaccine Ontology ID: VO_0000627
• Type: Subunit vaccine
• Antigen: Haemophilus b capsular polysaccharide (polyribosyl-ribitol-phosphate, PRP)
• Preparation: H. influenzae type b vaccine, coded as M1 and M2, respectively, was prepared for this trial in Boston and bottled in ten-dose vials (BenVenue Laboratories, Inc., Ohio). The lyophilized vaccine was kept at -20 C; after reconstitution with sterile, pyrogen-free water is was kept at + 4 C and used within eight hours (Peltola et al., 1977).

Human Response

• Vaccination Protocol: A total of 98,272 Finnish children, or 75.5% of the 130,178 children between the ages of 3 months to 5 years in the area, were vaccinated in three provinces in Finland. The campaign took place within two weeks in November 1974. A booster dose was given three months later to those who had been 3 to 17 months old at the time of the primary vaccination. The participation in the booster vaccination was 73.3%. Every other child (total, 49,295) received the group A meningococcal vaccine, every other (total, 48,977) the H. influenzae type b vaccine, coded as M1 and M2, respectively: All age groups and both sexes were equally represented. The dose of H. influenzae type b was 12.7 ug of polysaccharide in a volume of 0.5 ml except for the smallest infants (ages 3 to 5 months) who received only half of this dose. The subcutaneous injection was given by needle and syringe, usually into the upper part of the right arm. Children with an acute febrile disease, extensive eczema, or symptomatic asthma were not vaccinated (Peltola et al., 1977).
• Persistence: The serum antibodies induced by the vaccination proved short-lived (less than 6 months) in the infants younger than 18 months. Elevated serum antibody levels were detectable for 1and half year but less than 3 and half years in the children who were vaccinated when 18 to 35 months old. In the children who were 3 to 5 years old when vaccinated, the elevated anti-H influenzae type b capsular polysaccharide levels persisted for at least 3 and half years (Kayhty et al., 1984).
• Immune Response: The serum antibody response to the H. influenzae type b polysaccharide, measured by radioimmunoassay, was poor in children below 18 months of age and good in those above it. No effect of the vaccine could be seen on the nasopharyngeal carriage of H. influenzae type b, which was approximately 6% in this age group (Peltola et al., 1977).
• Side Effects: Adverse effects of the vaccine were mild
• Efficacy: The protection as well as senim antibody response was strongly age-dependent. Among children who had received the H. influenwe type b vaccine when 18 months of age or older, there were no cases of bacteremic disease caused by H. influenzae type b in the first year after vaccination. At the same time 1 1 such cases were seen in the control group of the same age, a highly significant difference. In the second year after vaccination two cases occurred in the H. influenzoe type b-vaccinated group, five in the meningocoecal-group A vaccinated group. No protection Was seen among children who had been younger than 18 months when vaccinatedı even if they received a booster dose of the vaccine.