Limited Serotypes of Pathogenic Bacteria Cause Pneumococcal Disease

The group of serotypes of Streptococcus pneumoniae responsible for most invasive pneumococcal disease worldwide is conserved across regions.

Serotype or serovar refers to distinct variations within a subspecies of bacteria or viruses. These microorganisms, viruses, or cells are classified together based on their cell surface antigens. The process of serotyping, determining serotypes can be based on a variety of factors.

Information on 60,090 isolates of S. pneumoniae from 70 countries was reviewed in a study carried out at the Johns Hopkins University Bloomberg School of Public Health, (Baltimore, MD, USA). The authors estimated which serotypes caused invasive pneumococcal disease among children under five in different regions of the world. They found that found seven serotypes (1, 5, 6A, 6B, 14, 19F, and 23F) were the most common globally and that these seven serotypes accounted for the majority of invasive pneumococcal disease in every region. These seven serotypes accounted for more than 300,000 deaths in Africa and 200,000 deaths in Asia. Serotypes included in both the 10- and 13-valent pneumococcal vaccines accounted for 10 million cases and 600,000 deaths worldwide.

The serotypes currently included in existing pneumococcal conjugate vaccine formulations account for 49% - 88% of deaths in children under five years old in Africa and Asia, where the morbidity and mortality of pneumococcal disease are the highest, and where until recently, most children do not have access to current pneumococcal conjugate vaccines.

The authors concluded that the findings contradict the conventional supposition that the most common serotypes causing invasive pneumococcal disease vary greatly across geographic regions. Recent progress towards increasing access to pneumococcal conjugate vaccines in high-burden countries will contribute to achieving the year 2015 Millennium Development Goal 4 target to reduce child mortality by two-thirds. The study was published on line in October 2010, in PLoS Medicine.

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