Immunogenicity for 16 serotypes of a unique schedule of pneumococcal vaccines in a high-risk population

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• A specialized vaccination schedule using 7-valent pneumococcal conjugate vaccine (7PCV) and 23-valent pneumococcal polysaccharide vaccine (23PPV) was implemented for Australian Aboriginal infants in 2001.
• This schedule involved 7PCV at 2, 4, and 6 months, followed by 23PPV at 18 months.

Purpose of the Study:

• To assess the immunogenicity of the 7PCV and 23PPV vaccination schedule in Australian Aboriginal infants.
• To determine anti-capsular IgG concentrations in vaccinated infants compared to a historic control group.

Main Methods:

• Anti-capsular IgG concentrations were measured using a blinded, (22F absorbed) ELISA.
• Vaccinated infants were compared against non-vaccinated historic control infants.
• Measurements were taken one month after the third dose of 7PCV and one month after the 23PPV dose.

Main Results:

• Following three doses of 7PCV, geometric mean concentrations (GMCs) exceeded 1.95 microg/ml, with over 89% of infants achieving IgG levels >0.35 microg/ml for all 7 serotypes.
• One month post-23PPV, more than 96% of infants had IgG >0.35 microg/ml to 7PCV serotypes, and over 50% had IgG >0.35 microg/ml to non-7PCV serotypes (including 6A, but not 12F or 19A).
• High IgG levels were sustained for the 7PCV serotypes after the 23PPV booster.

Conclusions:

• The 7-valent pneumococcal conjugate vaccine (7PCV) and 23-valent pneumococcal polysaccharide vaccine (23PPV) demonstrate significant immunogenicity in Australian Aboriginal infants.
• The implemented vaccination schedule effectively elicits protective antibody responses against key pneumococcal serotypes in this population.