Epidemiology and Infection

Original Papers

Trends in incidence of pneumococcal disease before introduction of conjugate vaccine: South West England, 1996–2005

C. A. IHEKWEAZUa1a2 c1, D. A. B. DANCEa1, R. PEBODYa3, R. C. GEORGEa3, M. D. SMITHa4, P. WAIGHTa3, H. CHRISTENSENa1, K. A. V. CARTWRIGHTa1 and J. M. STUARTa1

on behalf of the South West Pneumococcus Study Group

a1 Health Protection Agency, South West, Stonehouse, Stroud, Gloucestershire, UK

a2 European Programme for Intervention Epidemiology Training, EPIET, Smittskyddsinstitutet/EPI, Nobels väg 18, 171 82, Solna, Sweden

a3 Health Protection Agency, Centre for Infection, London, UK

a4 Taunton and Somerset NHS Trust, Musgrove Park Hospital, Taunton, Somerset, UK

Abstract

Introduction of pneumococcal conjugate and polysaccharide vaccines into the United Kingdom's routine immunization programmes is expected to change the epidemiology of invasive pneumococcal disease (IPD). We have documented the epidemiology of IPD in an English region (South West) with high-quality surveillance data before these programmes were established. We analysed data on isolates of Streptococcus pneumoniae from blood and CSF between 1996 and 2005 from microbiology laboratories in the South West that were reported and/or referred for serotyping to the Health Protection Agency Centre for Infections. The mean annual incidence of IPD increased from 11·2/100 000 in 1996 to 13·6/100 000 in 2005 (P<0·04). After adjusting for annual blood-culture sampling rates in hospitals serving the same catchment populations, an increase in annual incidence of IPD was no longer observed (P=1·0). Variation in overall incidence between laboratories could also be explained by variation in blood culture rates. The proportion of disease caused by serotypes 6B, 9V and 14 decreased significantly (P=0·001, P=0·007, and P=0·027 respectively) whereas that caused by serotype 4, 7F and 1 increased (P=0·001, P=0·003, and P<0·001 respectively) between 2000 and 2005. The level of penicillin non-susceptibility and resistance to erythromycin remained stable (2% and 12% respectively). This study provides an important baseline to assess the impact of changing vaccination programmes on the epidemiology of IPD, thus informing future use of pneumococcal vaccines.

(Accepted September 10 2007)

(Online publication October 26 2007)

Correspondence:

c1 Author for correspondence: Dr C. Ihekweazu, Health Protection Agency, South West, The Wheelhouse, Bonds Mill, Stonehouse, Stroud GL10 3RF, UK. (Email: chikwe.ihekweazu@hpa.org.uk)

Footnotes

† Members of the South West Pneumococcus Study Group are given in the Appendix.

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