Immunogenicity of Conjugate Pneumococcal Vaccine

New vaccines against Streptococcus pneumoniae, which is the leading cause of invasive diseases, are important advances in improving childhood health. Following the introduction of heptavalent pneumococcal conjugate vaccine to the national vaccine schedule in more than 30 countries, evaluation of immunogenicity of the vaccines has been an important procedure to carry out. The concentration of 0.35 microg/ml is suggested as the protective threshold against invasive disease. The additional absorption of the sera with pneumococcal type 22F polysaccharide makes the test more specific for the pneumococcal antibody concentration and correlates well with protective threshold levels of 0.20 microg/ml. The protective threshold levels for seropositivity of a child with post primary vaccination were; ELISA test specific for antibodies to vaccine-type capsular polysaccharides ≥0.05 μg/ml, opsonophagocytic activity ≥1: 8 and anti-PD antibody levels ≥100 EL. U/ml. The antibody level against Protein D is reported to be protective against otitis media due to nontypeable Haemophilus influenzae.By adding pneumococcal serotypes 1-5-7F to vaccine, vaccine coverage was increased up to 80% and could prevent otitis media and pneumoniae as well as IPD. Clinical studies demonstrated non-inferiority to PCV7 and no interference with coadministered vaccines.