Abstract
BackgroundDifferences in pathogenicity between pneumococcal serotypes are important when assessing the potential benefit of different valency vaccines. We investigated the effect of serotype on clinical presentation, outcome, and quality of life lost from invasive pneumococcal disease (IPD) in the context of the 7, 10, and 13 valent pneumococcal conjugate vaccines (PCV7, PCV10, PCV13).MethodSerotyped IPD cases in England were linked to the national dataset of hospital admissions for April 2002 to March 2011. Based on patients’ diagnostic codes and vital status at the end of the admission, disease focus (meningitis, empyema, sepsis, or respiratory disease) and case fatality rates by serotype and age group (5, 5–64, and 65 years and over) were obtained. Using these data the quality adjusted life years (QALY) lost from the IPD remaining when use of PCV7 stopped in 2010 was estimated for the serotypes covered by higher valency vaccines.ResultsThe linked dataset contained 23,688 cases with information on diagnosis, mortality, and serotype. There were significant differences between serotypes in the propensity to cause meningitis, death, and QALY loss in each of the investigated age groups. As a result, vaccines’ coverage of disease burden differed by endpoint. For example, in children under 5 years in 2009/10, PCV10 covered 39% of meningitis, 19% of deaths and 28% of the QALY loss of attributable to IPD, whereas the respective percentages for PCV13 were 65%, 67%, and 66%. The highest QALY loss per serotype in this age group was for 6A. Non-PCV serotypes causing the highest QALY loss were 22F and 33F in <5 year olds and 31 in older individuals.ConclusionMarked differences exist between serotypes in clinical presentation and outcome, and these should be considered when evaluating the potential impact of higher valency vaccines on overall disease burden and associated QALY loss.
Highlights
Streptococcus pneumoniae is a commonly carried bacterium that causes both invasive and non-invasive disease
Marked differences exist between serotypes in clinical presentation and outcome, and these should be considered when evaluating the potential impact of higher valency vaccines on overall disease burden and associated quality adjusted life years (QALY) loss
Since capsular differences between serotypes have been linked to such properties as carriage prevalence [2,3], propensity to cause invasive disease [4,5,2], and case fatality [6,7,8], each serotype could theoretically be regarded as a separate pathogen [4]
Summary
Streptococcus pneumoniae is a commonly carried bacterium that causes both invasive and non-invasive disease. Differences in the pathogenicity and clinical impact of different serotypes are important from a public health perspective because available vaccines are serotype-specific, and only target a small subset of the known serotypes. Introduction of the first pneumococcal conjugate vaccine that protected against seven of the most common serotypes in developed countries (PCV7) had a profound effect on serotype-specific carriage prevalence and caused replacement of vaccine types by serotypes not included in the vaccine [9,3,10,11]. The overall impact of this change in carriage prevalence on pneumococcal-attributable morbidity and mortality is dependent on the inherent pathogenicity of the replacing serotypes compared with the previously predominant vaccine types. We investigated the effect of serotype on clinical presentation, outcome, and quality of life lost from invasive pneumococcal disease (IPD) in the context of the 7, 10, and 13 valent pneumococcal conjugate vaccines (PCV7, PCV10, PCV13)
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