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Finnish efficacy trials with Haemophilus influenzae type b vaccines
Insights
The first Haemophilus influenzae type b (Hib) vaccine trial in Finland showed 90% efficacy in older children. Newer conjugate vaccines are also highly effective in infants.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Immunology
Background:
- The first Finnish trial (1973-1974) evaluated polysaccharide vaccines against Haemophilus influenzae type b (Hib).
- Polysaccharide-protein conjugate vaccines, developed later, offer improved immunogenicity.
- Randomized trials since 1986 have focused on conjugate Hib vaccine efficacy.
Purpose of the Study:
- To assess the efficacy of polysaccharide-protein conjugate Hib vaccines in infants.
- To compare the efficacy of PRP-D and HbOC conjugate vaccines.
Main Methods:
- A large-scale infant trial of the PRP-D conjugate vaccine was conducted.
- A comparative trial between PRP-D and HbOC vaccines was performed in 1988-1989.
Main Results:
- The polysaccharide vaccine was 90% efficacious in children aged 18-24 months.
- The PRP-D conjugate vaccine demonstrated 90% efficacy when administered to infants at 3, 4, and 6 months.
- Both PRP-D and HbOC vaccines appear efficacious after two infant doses, with ongoing follow-up.
Conclusions:
- Early polysaccharide Hib vaccines were effective in older children.
- Modern conjugate Hib vaccines, such as PRP-D and HbOC, are highly efficacious in infants.
- Infant vaccination with conjugate Hib vaccines is a critical strategy for preventing Hib disease.
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.