Pneumococcal Disease In Children

In follow up to our discussion of pneumococcal conjugate vaccines yesterday, we thought readers would benefit from a brief review of the diseases that these vaccines are designed to prevent.

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.