Streptococcus pneumoniae serotypes and vaccine formulations

Streptococcus pneumoniae Streptococcus pneumoniae is the leading bacterial cause of pneumonia, sepsis and meningitis in children, which together comprise more than 25% of the 10 million deaths estimated to have occurred in 2000 in children under 5 years of age, and preventable by access to appropriate vaccines. The serotypes currently included in existing pneumococcal conjugate vaccine formulations account for 49-88% of deaths in children under 5 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.

Contrary to current thinking, the group of serotypes of S. pneumoniae responsible for most invasive pneumococcal disease worldwide is conserved across regions. After an extensive literature review, which included information on 60,090 isolates of Streptococcus pneumoniae from 70 countries, the authors of a new paper estimate that 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.

This is good news. These findings mean that health policy makers can assess the potential impact of serotypes included in different conjugate vaccines and vaccine manufacturers can now work from a consensus set of serotype coverage estimates to plan and design future serotype-based vaccine formulations to target local pneumococcal disease burden more accurately. 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.

Systematic Evaluation of Serotypes Causing Invasive Pneumococcal Disease among Children Under Five: The Pneumococcal Global Serotype Project. (2010) PLoS Med 7(10): e1000348. doi:10.1371/journal.pmed.1000348
Background: Approximately 800,000 children die each year due to pneumococcal disease and .90% of these deaths occur in developing countries where few children have access to life-saving serotype-based vaccines. Understanding the serotype epidemiology of invasive pneumococcal disease (IPD) among children is necessary for vaccine development and introduction policies. The aim of this study was to systematically estimate the global and regional distributions of serotypes causing IPD in children ,5 years of age.
Methods and Findings: We systematically reviewed studies with IPD serotype data among children, 5 years of age from the published literature and unpublished data provided by researchers. Studies conducted prior to pneumococcal conjugate vaccine (PCV) introduction, from 1980 to 2007, with 12 months of surveillance, and reporting 20 serotyped isolates were included. Serotype-specific proportions were pooled in a random effects meta-analysis and combined with PD incidence and mortality estimates to infer global and regional serotype-specific PD burden. Of 1,292, studies reviewed, 169 were included comprising 60,090 isolates from 70 countries. Globally and regionally, six to 11 serotypes accounted for 70% of IPD. Seven serotypes (1, 5, 6A, 6B, 14, 19F, 23F) were the most common globally; and based on year 2000 incidence and mortality estimates these seven serotypes accounted for 300,000 deaths in Africa and 200,000 deaths in Asia. Serotypes included in both the 10- and 13-valent PCVs accounted for 10 million cases and 600,000 deaths worldwide.
Conclusions: A limited number of serotypes cause most IPD worldwide. The serotypes included in existing PCV formulations account for 49%–88% of deaths in Africa and Asia where PD morbidity and mortality are the highest, but few children have access to these life-saving vaccines.

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