Pneumonia is the leading cause of death in children under five years of age worldwide, mainly in developing countries; Streptococcus pneumoniae is found to be the most common infectious pathogen of the disease. Pneumococcal conjugate vaccines (PCVs) for infants have been introduced in many national immunisation programmes, and their use has been recommended worldwide. In 2015, a 10-valent PCV has been introduced in Bangladesh's national immunisation programme. Our aim was to identify the most prevalent pneumococcal serotypes causing pneumonia in children in Bangladesh, and to calculate reference ranges for serotype-specific antibody concentrations. 1533 children aged 1 to 59 months diagnosed with WHO-defined pneumonia at an urban health care facility in the Kamalapur area in Dhakawere enrolled between October 2011 and January 2014. Two serum samples were collected from all participants, and the serotype-specific pneumococcal antibody response was measured using an immunoassay panel of 25 specifically selected serotypes (1, 2, 3, 4, 5, 6A, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12A, 12F, 14, 15B, 18C, 19A, 19F, 20, 22F, 23F, 33F and 45). By calculating the fold increase of all antibodies between the second and first sample, serotype-specific pneumococcal disease could be identified. A serotype-specific antibody response was detected in 473 (31 percent) participants. The 10 most frequently identified serotypes in descending order were: 11A, 22F, 3, 2, 19F, 45, 15B, 19A, 33F, and 9N. Out of these, only 19F, and potentially 19A by cross-reactivity, are covered by PCV10. This suggests that serotype coverage of the 10-valent PCV implemented in Bangladesh is low for the most prevalent serotypes.
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