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Clinical studies of pneumococcal vaccines in infants. I. Reactogenicity and immunogenicity of two polyvalent
Insights
Two polyvalent pneumococcal vaccines were tested in infants. Neither vaccine showed optimal immunogenicity, suggesting modifications are needed for improved infant immune responses.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Pneumococcal infections pose a significant health risk to infants.
- Development of effective polyvalent pneumococcal vaccines is crucial for infant health.
- Previous studies have explored various vaccine formulations and schedules.
Purpose of the Study:
- To evaluate the immunogenicity and safety of two different polyvalent pneumococcal vaccines in infants.
- To compare antibody responses elicited by octavalent and 14-valent pneumococcal vaccines.
- To assess the impact of vaccination timing (6 vs. 12 months) on antibody titers and persistence.
Main Methods:
- Randomized controlled trial involving infants at 6 and 12 months of age.
- Administration of octavalent or 14-valent pneumococcal vaccines or placebo.
- Serum collection at multiple time points (6, 7, 12, 13, 24 months) to determine geometric mean titers (GMTs).
- Monitoring of clinical reactions post-vaccination.
Main Results:
- Octavalent vaccine showed significant immunogenicity against specific Streptococcus pneumoniae types when administered at 6 or 12 months.
- 14-valent vaccine demonstrated immunogenicity against certain types when given at 12 months.
- Vaccination at 6 months resulted in lower GMTs upon revaccination.
- Unvaccinated controls showed natural antibody acquisition.
- All groups had similar GMTs by 24 months.
- Clinical reactions were mild and transient.
Conclusions:
- Current octavalent and 14-valent pneumococcal vaccines exhibit limited immunogenicity in infants.
- Vaccination timing may influence immune responses, with potential suppression observed when given at 6 months.
- Further modifications to vaccine formulations or schedules are necessary to enhance infant immunogenicity against Streptococcus pneumoniae.
Abstract:
Normal infants, selected at six months of age for participation in one of two separate studies of polyvalent pneumococcal vaccines, octavalent vaccine for Eli Lilly Laboratories (Indianapolis, Ind.) and 14-valent vaccine from Merck Sharp & Dohme (West Point, Pa.), were assigned randomly to groups to receive vaccine at six and/or 12 months of age or to control (unvaccinated) groups. Serum collected at ages six, seven, 12, 13, and 24 months provided pre- and postvaccination geometric mean titers (GMTs) as well as information about persistence of antibody titers. Clinical reactions were monitored by a home visit at 24 hr after each injection. The octavalent vaccine, when given at six months of age, stimulated significant antibody against Streptococcus pneumoniae type 3 and against types 3, 7, 18, and 23 when given at 12 months of age; GMTs were significantly higher than those of controls of the same ages (P less than or equal to 0.05). The 14-valent product, given at 12 months of age, was immunogenic against types 6, 7, 8, and 14 when GMTs were compared with those of controls (P less than or equal to 0.05). Vaccination at six months of age was followed by depressed GMTs on revaccination. Natural acquisition of antibody was indicated by rising GMTs in the unvaccinated controls, who had an increase of greater than or equal to 1.8-fold for all types during the interval between six and 13 months of age. By the age of 24 months, GMTs of all groups were similar. Clinical reactions were mild and brief (less than or equal to 36 hr). Results of these studies indicate that modification of the vaccines is needed for improvement of the immunogenicity in infants.