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Haemophilus influenzae type b conjugate vaccine (meningococcal protein conjugate): immunogenicity and safety at
R Yogev1, M Arditi, E G Chadwick
1Dept of Pediatrics, Children's Memorial Hospital, Northwestern University Medical School, Chicago, IL 60614.
Insights
The Haemophilus influenzae type b (Hib) vaccine showed varied efficacy. Newer conjugate vaccines like PRP-D are more immunogenic but still have limitations in infants, necessitating further research for optimal protection strategies.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- The purified capsular polysaccharide (PRP) vaccine for Haemophilus influenzae type b (Hib) demonstrated 90% efficacy in Finnish children over 18 months but showed inconsistent results in the United States.
- PRP vaccine was ineffective in children under 18 months, the age group most affected by Hib meningitis.
Purpose of the Study:
- To evaluate the efficacy and immunogenicity of Haemophilus influenzae type b vaccines, specifically comparing the polysaccharide vaccine (PRP) with newer conjugate vaccines (PRP-D).
- To address discrepancies in PRP vaccine efficacy and investigate the protective potential of PRP-D in infants.
Main Methods:
- Review of efficacy estimates for PRP vaccine in Finland and the United States.
- Assessment of immunogenicity data for PRP-D conjugate vaccines in infants of various ages.
- Analysis of reported protective efficacy of PRP-D in a vaccination schedule including early infant doses.
Main Results:
- PRP vaccine efficacy estimates varied widely in the US (-55% to +89%) compared to Finland (90%).
- PRP-D conjugate vaccines are more immunogenic than PRP vaccines across all age groups.
- Two doses of PRP-D in 7-month-old infants induced antibody levels comparable to older infants receiving PRP alone.
- Repeat PRP-D vaccinations at 3, 4, 6, and 14 months showed 83% protective efficacy, but low antibody levels were observed in infants younger than 7 months.
Conclusions:
- Discrepancies in PRP vaccine efficacy and limited data on PRP-D in US infants led to its recommendation only for children 18 months and older.
- Further research is needed to understand the protective efficacy of PRP-D in younger infants and reconcile efficacy data across different regions.
Abstract:
The Haemophilus influenzae vaccine consisting of purified type b capsular polysaccharide (polyribosylribitol-phosphate [PRP]) was shown in Finland to be protective, with 90% efficacy in children older than 18 to 23 months of age. However, a wide range of estimates of vaccine efficacy has been reported in the United States after its licensure in 1985. These estimates range from -55% to +89%. In addition, the PRP vaccine was not effective in children younger than 18 months of age, in whom 70% to 80% of meningitis cases occur. A further development was the introduction of H influenzae type b polysaccharide-protein conjugate vaccines such as the PRP-D. These conjugate vaccines were found to be more immunogenic than PRP vaccine in children of all ages. Two doses of PRP-D in infants 7 months of age and older induced antibody levels equal to or greater than levels in infants 24 months of age who received the PRP vaccine alone. Recently, Eskola et al reported that repeat vaccinations with PRP-D at 3, 4, 6, and 14 months of age was 83% protective (95% confidence interval, 26% to 96%). Yet PRP-D vaccine elicits only low serum antibody levels in infants younger than 7 months of age. Because of the discrepancy in efficacy results for the PRP vaccine in the United States and Finland and the lack of data about the protective efficacy of PRP-D vaccine in infants in the United States, the PRP-D vaccine is currently recommended only for children 18 months of age or older.(ABSTRACT TRUNCATED AT 250 WORDS)