Pneumococcal conjugate vaccine (Prevnar; PNCRM7): a review of its use in the prevention of Streptococcus pneumoniae infection

PNCRM7 (Prevnar) is a pneumococcal vaccine containing seven capsular polysaccharide antigens from the bacterium Streptococcus pneumoniae, each of which is conjugated to diphtheria protein [cross-reactive material (CRM(197))]. CRM(197) is an inert but immunogenic variant of diphtheria toxoid that is also used as a carrier molecule in one Haemophilus influenzae type b conjugate vaccine. Unlike the 23-valent unconjugated pneumococcal vaccines, PNCRM7 elicits a T cell-dependent response and thus protects young children against pneumococcal disease. The immunogenicity of PNCRM7 has been demonstrated in both healthy children aged <2 years and older children in high-risk groups. Two randomized, double-blind trials conducted in the US demonstrated that all PNCRM7 serotypes were immunogenic in healthy infants and young children when compared with a control vaccine. A booster dose of PNCRM7 elicited an anamnestic response to all seven serotypes. Data from a large, randomized, double-blind study conducted in California (US) have confirmed the protective efficacy of PNCRM7 against invasive pneumococcal disease (e.g. bacteremia, meningitis) caused by serotypes included in the vaccine. The vaccine efficacy in the per-protocol analysis was 97.4% and its efficacy against invasive disease caused by any pneumococcal serotype in the intent-to-treat (ITT) analysis was 89.1%. Indeed, a postlicense surveillance study (n = 211,565) showed that the introduction and routine use of PNCRM7 was associated with a marked reduction in invasive pneumococcal disease in children <5 years of age. In addition, the US trial and another randomized, double-blind trial conducted in Finland, showed that PNCRM7 vaccine efficacy against all otitis media episodes was between 6 and 7%. PNCRM7 vaccine was generally well tolerated and had a similar local and systemic adverse events profile to other pediatric vaccines. The most common local adverse event associated with PNCRM7 administration was inflammation at the injection site, and the most common systemic adverse effect was febrile illness (> or =38 degrees C) that usually resolved without treatment. The limited available pharmacoeconomic data suggest that PNCRM7 could be cost effective depending, in part, on the manufacturer's list price of the vaccine. Results of the base case analysis in a US study showed a cost-effectiveness ratio for PNCRM7 of US dollars 80,000 per life-year saved from a societal perspective compared with US dollars 176,000 from a healthcare payer perspective, assuming a nondiscounted list price of US dollars 58 per dose (1997 costs). Concomitant administration of PNCRM7 vaccine with hepatitis B, oral polio, meningococcal oligosaccharide protein conjugate or H. influenzae type b vaccines did not affect the immunogenicity of these pediatric vaccines to a clinically relevant extent.

CONCLUSION

PNCRM7 vaccine will be of great benefit to those societies that have active immunization programs implemented. In infants and vulnerable children throughout the world, PNCRM7 vaccine has the potential to reduce the mortality and morbidity rates associated with S. pneumoniae infections. In developed countries, the vaccine will be of particular benefit in preventing disabling infections but its impact in developing countries will be more pronounced with the potential to greatly reduce mortality.