Finnish efficacy trials with Haemophilus influenzae type b vaccines

Abstract

The first Finnish trial with Haemophilus influenzae type b vaccine was conducted during 1973-1974. It demonstrated that the polysaccharide vaccine was 90% efficacious in children greater than or equal to 18-24 months old. The immunologically superior polysaccharide-protein conjugate vaccines have been used since 1986 in randomized trials. The PRP-D vaccine (polysaccharide conjugated to diphtheria toxoid) was 90% efficacious when given at 3, 4, and 6 months of age to 58,000 infants. In 1988-1989, the PRP-D vaccine was compared with the HbOC vaccine (oligosaccharide conjugated to CRM197 protein). Follow-up is continuing, but both vaccines seem to be efficacious after two doses in infancy.