Trends and geographical variation in invasive pneumococcal infections in Finland

Abstract

We evaluated regional variation and trends in invasive pneumococcal infections (IPI) in Finland by using data from national, population-based laboratory surveillance and number of blood and cerebrospinal fluid (CSF) cultures performed by all microbiology laboratories during 1995-2002. The overall annualized IPI incidence was 10.6/100,000 (range by region, 7.9 15.1): 9.9 for bacteraemias (range 7.3-14.2) and 0.6 for meningitis (range 0.4-1.1). The rate in children aged <5 y was 23.5/100,000. Regional pneumococcal bacteraemia rates were correlated with blood culture sampling rates (p =0.015), but meningitis rates did not correlate with CSF culture rates. During 1995-2002, the overall annual IPI rate increased by 35.1%, from 8.2 to 11.5/100,000 (p<0.001). The annual blood culturing rate increased by 29.6% (p=0.015 for the correlation with IPI rate). Temporal increase and higher regional IPI rates were significantly associated with higher blood culturing rates. Pneumococcal serotypes included in the 7- and 10-valent conjugate vaccines caused 69.8% and 85.2% of IPIs among children aged <5 y and 49.5% and 59.3% in adults, respectively. The true incidence of pneumococcal bacteraemia in Finland may be higher than previously estimated. Introduction of universal childhood pneumococcal conjugate immunization would provide substantial health benefits to Finnish children and adults.