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By Joanna Lyford, Senior medwireNews Reporter

The incidence of invasive pneumococcal disease (IPD) in Taiwan has decreased significantly in recent years, study findings indicate.

This decline has been accompanied by a reduction in the annual incidence of several Streptococcus pneumoniae serotypes, including 14, 23F, and 6B, whereas serotype 19A has increased significantly, particularly among children.

“[T]he emergence of serotype 19A, especially in children in Taiwan may be due to inadequate coverage of vaccination,” say the study authors, who call for closer monitoring of trends in pneumococcal serotypes and for vaccination programmes to be adjusted accordingly.

Po-Ren Hsueh (National Taiwan University Hospital, Taipei) and co-workers obtained information on all cases of IPD seen at a medical centre in northern Taiwan between January 2000 and December 2012.

Over this period, the annual incidence of IPD fell from 9.8 to 2.1 cases per 10,000 admissions, a highly significant reduction.

Analysis of individual pneumococcal diagnoses revealed significant reductions in the incidence of all-cause bacteraemia, primary bacteraemia, bacteraemic pneumonia, peritonitis and meningitis.

These “encouraging” findings can be attributed to the introduction of two conjugated vaccines, say the authors in BMC Infectious Diseases.

While the incidence of several serotypes declined (14, 23F, 6B) or were unchanged (3 and 19F) during the study period, both the incidence and the proportion of serotype 19A increased significantly.

Overall, serotype 19A of S. pneumoniae accounted for 10.9% of isolates causing IPD in adults and 10.1% in children.

Remarkably, in children, the annual incidence of serotype 19A rose from less than 5% between 2000 and 2008 to approximately 75% between 2011 and 2012. This serotype is susceptible to a vaccine that is currently used only in people aged 65 years and over, the authors remark.

They conclude that IPD caused by serotype 19A of S. pneumoniae is an “emerging problem” in Taiwan and conclude: “[O]ur findings suggest that the secular trend in pneumococcal serotype distribution needs to be closely monitored and that the use of vaccination needs to be adjusted according to the change in serotype distribution.”

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