Serum opsonic activity in infants with sickle-cell disease immunized with pneumococcal polysaccharide protein conjugate vaccine

Pneumococcal infections are an important cause of morbidity and mortality i n children with sickle-cell disease (SCD), Pneumococcal conjugate vaccines (PCVs) are immunogenic in healthy infants <2 years of age but have not been evaluated in young children,vith SCD. Infants with SCD were immunized with a 7-valent PCV (Wyeth-Lederle Vaccines & Pediatrics) at 2, 4, and 6 months of age. A booster dose of 23-valent pneumococcal polysaccharide vaccine (P PV; Pnu-Immune) was administered at 24 months of age. Antipneumococcal type 6B and 14 serum opsonic activity was measured to assess the biologic funct ion of the antibody. Following the administration of three doses of PCV, op sonic activity against serotype 6B increased from 4.8% at 2 months to 33.5% at 7 months, with a subsequent decline to 8.1% at 12 months and 7.5% at 24 months and with an increase to 30.7% at 25 months after administration of a booster dose of PPV. Similar trends were seen with serotype 14 (opsonic a ctivities were 9.4% at 2 months, 24.9% at 7 months, 16.5% at 12 months, and 12.6% at 24 months, and the opsonic activity was 27.3% 1 month after the a dministration of PPV). Serum opsonic activity correlated with antibody leve ls for both serotypes, PCV induces serum opsonic activity in infants with S CD, Antipneumococcal serum opsonic activity correlates with antibody levels .