Clinical Presentations
Streptococcus pneumoniae causes acute bacterial infections. Also referred to as the pneumococcus bacteria, it was first isolated by Pasteur in 1881. Prior to the introduction of Prevnar, this bacteria was the most common cause of invasive bacterial infections and acute otitis media (middle ear infections) in North America. Sinusitis, pneumonia, and conjunctivitis are all commonly caused by S. pneumoniae and it remains one of the two most common causes of bacterial meningitis in infants and young children.
Invasive pneumococcal disease (IPD) is defined as the isolation of S. pneumonieae from a normally sterile site (CSF, blood, joint fluid, etc.). For example, bacteremia and meningitis are examples of IPD while otitis media and conjunctivitis are not.

Epidemiology
Pneumococci commonly colonize the upper respiratory tract of adults and children. Bacteria are spread person to person by contact with respiratory droplets. Within one month of acquiring the bacteria in the upper respiratory tract about 15% of children will develop disease. Infections are more common in winter months and certain populations are at higher risk including infants, young children, the elderly, black, Alaskan Native and some American Indian populations. Individuals with congenital or acquired immunodeficiency, absent or diminished splenic function, cochlear implants, and a number of other chronic conditions are at increased risk of disease as well. Since Prevnar’s introduction in the United States in 2000 the incidence of all invasive pneumococcal infections has decreased by 80% in children less than 2 years of age, and by 90% for those serotypes included in Prevnar. Corresponding decreases have also occurred in older children and adults as well, possibly due to the interruption of transmission from infants and young children to these older contacts. It should be noted that an increase in incidence of disease caused by serotypes not contained in Prevnar has occurred in some areas.

This overview of clinical presentations and epidemiology is helpful background to those trying to understand the potential impact of a new generation of pneumococcal vaccines, however, greater detail is required to compare and contrast the vaccines of interest. Make sure to visit us again as we explore the unique characteristics of these vaccines in greater detail and thanks for tuning in to the BioHorizon.

Since its approval in the United States in 2000 Wyeth’s Prevnar vaccine against pneumococcal disease has helped to transform what was thought of as a mature, marginally profitable segment of the pharmaceutical business into a much more dynamic and profitable one. Prevnar has proven to be both effective and innovative while filling an unmet need in the prevention of serious pediatric infections caused by the pneumococcal bacteria. According to CNN Money.com, Prevnar sales surged 24% in 2007 to $2.4 billion, making it the first vaccine to exceed $2 billion in annual sales.

Prevnar has been the only conjugate pneumococcal vaccine available to immunization programs and clinicians throughout North America and European Union looking to prevent pneumococcal disease. However, GSK’s new 10-valent conjugate pneumococcal vaccine (Synflorix) could soon start changing this.

There are two significant differences between Synflorix and Prevnar that our readers should be aware of. First, Prevnar contains antigen from seven different serotypes of pneumococcal bacteria while Synflorix contains antigen from ten different types. The second difference is in the carrier protein that these polysaccharide antigens are attached to. In Prevnar the protein is called CRM-197 and it has been critical in the success of Wyeth’s product. The carrier protein is more than a passive molecule, it greatly enhances the immunogenicity of the vaccine and makes it more effective. In Synflorix, the carrier protein (NTHi) not only does this, but because it is derived from non-typable Haemophilus Influenza bacteria, provides protection against infections with this pathogen as well. GSK has filed for Synflorix approval in the EU and the vaccine has recently been approved for sale in Canada but we have no word on when or even if approval will be sought in the United States.

The story does not end here as Wyeth is countering with an enhanced version of Prevnar that contains protection against thirteen different serotypes of the pneumococcal bacteria and has filed for approval in both the United States and the European Union.

There are some fundamental questions that need to be explored further concerning the safety and effectiveness of these new vaccines, the changing epidemiology of pneumococcal disease, and of course the cost-effectiveness data that is all important to vaccine program planners. Readers should stay tuned as we plan to explore these crtical areas in the coming days. Thanks for joining us today on the BioHorizon.