Trends in incidence of and serotypes causing invasive pneumococcal disease in Finland during 1995–2007: implications for introduction of conjugate vaccine

Abstract number: P1706

Nohynek H., Kaijalainen T., Ollgren J., Lyytikäinen O., Salo H., Klemets P., Nuorti P., Leinonen M., Ruutu P., Kilpi T.

Introduction: Pneumococcal (Pnc) conjugate vaccines (PCV) decrease vaccine type specific incidence of invasive Pnc disease (IPD) but also increase non-vaccine serotype IPD. How much such phenomena is caused by underlying secular trends and evolutionary processes irrespective of PCV use is not well known. In anticipation of PCV introduction into national immunisation programme, we analysed trends of IPD and causative serotypes in Finland during years 1995–2006.

Methods: Notifiable IPD was defined as clinical condition with Pnc isolated from normally sterile site (blood, CSF, other). Isolates were obtained from adults and children hospitalised for IPD. Pnc were serotyped using quellung, Latex and/or CIEP (antisera from StatensSerumInstitute, Denmark) in KTL Reference Laboratory.

Results: Total 7193 Pnc isolates were identified. During observation period, overall IPD incidence grew significantly (1.5-fold) from 9/100 000 in 1995 to 14/100 000 in 2006. Increase was significant in children <5 and adults >50 years. Strong seasonal pattern in IPD was observed with annual peaks December and May. In 2006, most common Pnc serotypes were 14, 4, 6B, 23F, 3, 7F, 9V and 19F constituting 70% of all isolates, although among children <5 serotypes 3, 4, 7F, and 9V were observed less frequently. Since 1995, proportion of serotypes 14 and 9V had significantly increased, 4 and 7F decreased, while proportion of others remained constant, as did composition of most prevalent serotypes in children <5 (i.e. 6B, 14, 19F, 23F, 18C, 19A). During observation period among children <2 years, coverage of 7PCV serotypes fluctuated between 47 and 81% (mean 70%). Among those >2 years, coverage of 7PCV serotypes increased significantly from 47 to 59% (p for trend 0.000).

In Table, range and mean % of vaccine serotype coverage among those to be vaccinated (<2 year olds) and those who might benefit from herd effect of PCV (>2 year olds), and p for linear trend of increase during 12 years of observation period.

While incidence of IPD has increased in past 12 years, seasonal pattern and constancy in composition of majority serotypes prevails with fluctuation in rank order of prevalent serotypes among children <2 years. In others, proportion of 7PCV and 10PCV serotypes has significantly increased.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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