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Bacterial meningitis in Finland, 1995-2014: a population-based observational study
Aleksandra Polkowska1, Maija Toropainen2, Jukka Ollgren2
1School of Health Sciences, University of Tampere, Lääkärinkatu, Tampere, Finland.
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.
Insights
Bacterial meningitis incidence declined significantly due to conjugate vaccines and secular trends. Ongoing surveillance is crucial for future vaccination strategies against this serious infection.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Bacterial meningitis remains a significant global health concern, causing substantial morbidity and mortality.
- Epidemiological patterns of bacterial meningitis are evolving due to factors like vaccination and societal changes.
- Finland introduced conjugate vaccines against Haemophilus influenzae type b (in 1986) and Streptococcus pneumoniae (in 2010).
Purpose of the Study:
- To assess the disease burden and long-term trends of five common bacterial meningitis pathogens in Finland.
- To evaluate the impact of conjugate vaccines and secular trends on bacterial meningitis epidemiology.
- To analyze changes in incidence rates, case fatality, and age distribution of bacterial meningitis cases.
Main Methods:
- A population-based observational study analyzed laboratory-confirmed bacterial meningitis cases from 1995-2014.
- Cases were defined by isolation of Streptococcus pneumoniae, Neisseria meningitidis, Streptococcus agalactiae, Listeria monocytogenes, or Haemophilus influenzae from cerebrospinal fluid.
- Statistical methods included Poisson or negative binomial regression for incidence rates and chi-squared tests for case fatality proportions.
Main Results:
- Streptococcus pneumoniae and Neisseria meningitidis comprised 78% of the 1361 cases studied.
- Overall bacterial meningitis rates decreased by 4% annually, from 1.88 to 0.70 cases per 100,000 person-years.
- Significant annual reductions were observed for Neisseria meningitidis (9%) and Streptococcus pneumoniae (2%), while the median age of cases increased.
Conclusions:
- Decreases in bacterial meningitis are linked to infant conjugate vaccination and a secular trend in meningococcal meningitis.
- Epidemiological surveillance is essential for monitoring trends, evaluating vaccine effectiveness, and informing future vaccination strategies.
- Continued monitoring is necessary to understand serotype distribution and adapt public health interventions for bacterial meningitis.
