Safety and immunogenicity of heptavalent pneumococcal vaccine conjugated to CRM(197) among infants with sickle cell disease. Pneumococcal Conjugate Vaccine Study Group.

OBJECTIVES: To determine the immunogenicity and safety of heptavalent pneumococcal polysaccharide vaccine (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to CRM(197) (7-valent conjugate pneumococcal vaccine [7VPnC]) among infants with sickle cell disease (SCD) and a comparison group of infants without SCD (non-SCD).
DESIGN: Two cohorts of infants were enrolled and received open-label doses of 7VPnC vaccine; infants enrolled before 2 months of age received 7VPnC vaccine at 2, 4, and 6 months of age followed by 23-valent pneumococcal polysaccharide vaccine (PS-23) at 24 months of age for those infants with SCD (schedule A), and infants enrolled between 2 and 12 months of age received 7VPnC at 12 months of age followed by PS-23 at 24 months of age for infants with SCD (schedule B). Safety data were collected for 3 days after each dose of vaccine. Antibody concentrations were measured to each of the 7VPnC serotypes by enzyme-linked immunosorbent assay before each vaccine dose and 1 month after the last 7VPnC dose and the PS-23 vaccine dose.
RESULTS: Forty-five infants (34 SCD and 11 non-SCD) were vaccinated according to schedule A and 16 infants (13 SCD and 3 non-SCD) according to schedule B. The 7VPnC vaccine was highly immunogenic for all serotypes among infants with and without SCD who received 3 doses of vaccine according to schedule A: depending on serotype, 89% to 100% achieved antibody concentrations above.15 microg/mL and 56% to 100% achieved antibody concentrations above 1.0 microg/mL. Among infants immunized according to schedule B, a single dose of 7VPnC vaccine resulted in antibody concentrations above.15 microg/mL in 53% to 92% by serotype and above 1.0 microg/mL in 31% to 71% by serotype. A single dose of PS-23 resulted in dramatic increases in the antibody concentrations to all serotypes regardless of 1- or 3-dose priming. There was no difference in the reactogenicity of the 7VPnC vaccine between those with and without SCD. There were no serious reactions to the 7VPnC or PS-23 vaccines, even among those with high antibody concentrations before immunization.
CONCLUSIONS: Infants with SCD respond to 7VPnC vaccine with antibody concentrations that are at least as high as infants without SCD. Infants immunized with 7VPnC vaccine at 2, 4, and 6 months of age developed antibody concentrations in the same range as those achieved among infants without SCD enrolled in a large trial that demonstrated vaccine efficacy against invasive disease. Significant rises were seen in antibody concentrations to all 7VPnC serotypes after the PS-23 booster in children receiving schedule A or B.