Objectives Bacterial meningitis remains an important cause of morbidity and mortality worldwide. Its epidemiological characteristics, however, are changing due to new vaccines and secular trends. Conjugate vaccines against Haemophilus influenzae type b and Streptococcus pneumoniae (10-valent) were introduced in 1986 and 2010 in Finland. We assessed the disease burden and long-term trends of five common causes of bacterial meningitis in a population-based observational study.
Methods A case was defined as isolation of S. pneumoniae, Neisseria meningitidis, Streptococcus agalactiae, Listeria monocytogenes or H. influenzae from cerebrospinal fluid and reported to national, population-based laboratory surveillance system during 1995–2014. We evaluated changes in incidence rates (Poisson or negative binomial regression), case fatality proportions (χ2) and age distribution of cases (Wilcoxon rank-sum).
Results During 1995–2014, S. pneumoniae and N. meningitidis accounted for 78% of the total 1361 reported bacterial meningitis cases. H. influenzae accounted for 4% of cases (92% of isolates were non-type b). During the study period, the overall rate of bacterial meningitis per 1 00 000 person-years decreased from 1.88 cases in 1995 to 0.70 cases in 2014 (4% annual decline (95% CI 3% to 5%). This was primarily due to a 9% annual reduction in rates of N. meningitidis (95% CI 7% to 10%) and 2% decrease in S. pneumoniae (95% CI 1% to 4%). The median age of cases increased from 31 years in 1995–2004 to 43 years in 2005–2014 (p=0.0004). Overall case fatality proportion (10%) did not change from 2004 to 2009 to 2010–2014.
Conclusions Substantial decreases in bacterial meningitis were associated with infant conjugate vaccination against pneumococcal meningitis and secular trend in meningococcal meningitis in the absence of vaccination programme. Ongoing epidemiological surveillance is needed to identify trends, evaluate serotype distribution, assess vaccine impact and develop future vaccination strategies.
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Contributors Study concept and design: AP, OL, PN. Acquisition of data: MT, JO, OL, PN. Analysis and interpretation of data: AP, MT, JO, OL, PN. Drafting of the manuscript: AP, PN. Critical revision of the manuscript for important intellectual content: AP, MT, JO, OL, PN. Statistical analysis: AP, JO. Obtained funding: PN. Study supervision: PN. Final approval: AP, MT, JO, OL, PN.
Funding This study was supported by the School of Health Sciences, University of Tampere and the National Institute for Health and Welfare (THL) in Helsinki, Finland.
Competing interests None declared.
Ethics approval Data used in the analysis were collected as a part of surveillance and infection control activities which falls under the existing mandate of the National Institute for Health and Welfare (THL).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional data are available.
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